CSS Text Module Level 3

CSS Text Module Level 3
CSS Text Module Level 3
W3C Candidate Recommendation Snapshot,
22 December 2020
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Latest published version:
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Editors:
Elika J. Etemad / fantasai
Invited Expert
Koji Ishii
Invited Expert
Florian Rivoal
Invited Expert
Suggest an Edit for this Spec:
GitHub Editor
Test Coverage Analysis:
W3C
MIT
ERCIM
Keio
Beihang
). W3C
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and
permissive document license
rules apply.
Abstract
This CSS module defines properties for text manipulation and specifies their processing model. It covers line breaking, justification and alignment, white space handling, and text transformation.
CSS
is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, etc.
Status of this document
This section describes the status of this document at the time of its publication.
Other documents may supersede this document.
A list of current W3C publications
and the latest revision of this technical report
can be found in the
W3C technical reports index at https://www.w3.org/TR/.
This document was published
by the
CSS Working Group
as a
Candidate Recommendation Snapshot
Publication as a Candidate Recommendation
does not imply endorsement by the W3C Membership.
A Candidate Recommendation Snapshot has received
wide review
and is intended to gather implementation experience.
This document is intended to become a W3C Recommendation;
it will remain a Candidate Recommendation at least until
22 February 2021
to gather additional feedback.
Please send feedback
by
filing issues in GitHub
(preferred),
including the spec code “css-text” in the title, like this:
“[css-text]
…summary of comment…
”.
All issues and comments are
archived
Alternately, feedback can be sent to the (
archived
) public mailing list
www-style@w3.org
This document is governed by the
15 September 2020 W3C Process Document
This document was produced by a group operating under the
W3C Patent Policy
W3C maintains a
public list of any patent disclosures
made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent which the individual believes
contains
Essential Claim(s)
must disclose the information in accordance with
section 6 of the W3C Patent Policy
This publication fully addresses the issues raised since the
October 2013 Last Call Working Draft
, which are documented in the
disposition of comments
The following features are at-risk, and may be dropped during the CR period:
the
full-width
value of
text-transform
the
full-size-kana
value of
text-transform
the values of the
tab-size
property
the
text-justify
property
the percentage values of
word-spacing
the
hanging-punctuation
property
Writing-system specific adjustments to line-breaking
Trimming trailing Ogham space marks
“At-risk” is a W3C Process term-of-art, and does not necessarily imply that the feature is in danger of being dropped or delayed. It means that the WG believes the feature may have difficulty being interoperably implemented in a timely manner, and marking it as such allows the WG to drop the feature if necessary when transitioning to the Proposed Rec stage, without having to publish a new Candidate Rec without the feature first.
1.
Introduction
This module describes the typesetting controls of CSS;
that is, the features of CSS that control the translation of
source text to formatted, line-wrapped text.
Various CSS properties provide control over
case transformation
white space collapsing
text wrapping
line breaking rules
and
hyphenation
alignment and justification
spacing
and
indentation
Note: Font selection is covered in
CSS Fonts Level 3
[CSS-FONTS-3]
Features for decorating text,
such as
underlines
emphasis marks
and
shadows
(previously part of this module)
are covered in
CSS Text Decoration Level 3
[CSS-TEXT-DECOR-3]
Bidirectional
and
vertical
text
are addressed in
CSS Writing Modes Level 3
[CSS-WRITING-MODES-3]
Further information about the typesetting requirements
of various languages and writing systems around the world
can be found in the
Internationalization Working Group
’s
Typography Index
[TYPOGRAPHY]
1.1.
Module Interactions
This module, together with
[CSS-TEXT-DECOR-3]
replaces and extends the text-level features defined in
[CSS2]
chapter 16.
In addition to the terms defined below,
other terminology and concepts used in this specification are defined
in
[CSS2]
and
[CSS-WRITING-MODES-3]
1.2.
Value Definitions
This specification follows the
CSS property definition conventions
from
[CSS2]
using the
value definition syntax
from
[CSS-VALUES-3]
Value types not defined in this specification are defined in CSS Values & Units
[CSS-VALUES-3]
Combination with other CSS modules may expand the definitions of these value types.
In addition to the property-specific values listed in their definitions,
all properties defined in this specification
also accept the
CSS-wide keywords
as their property value.
For readability they have not been repeated explicitly.
1.3.
Languages and Typesetting
Authors should accurately language-tag their content for the best typographic behavior.
Many typographic effects vary by linguistic context.
Language and writing system conventions can affect
line breaking, hyphenation, justification, glyph selection,
and many other typographic effects.
In CSS, language-specific typographic tailorings
are only applied when the
content language
is known (declared).
Therefore,
higher quality typography requires authors to communicate to the UA
the correct linguistic context of the text in the document.
The
content language
of an element is the (human) language
the element is declared to be in, according to the rules of the
document language
Note that it is possible for the
content language
of an element
to be unknown—
e.g. untagged content,
or content in a
document language
that does not have a language-tagging facility
is considered to have an unknown
content language
Note:
Authors can declare the
content language
using the global
lang
attribute in HTML
or the universal
xml:lang
attribute in XML.
See the
rules
for determining the content language of an HTML element
in
[HTML]
and the
rules
for determining the content language of an XML element
in
[XML10]
The
content language
an element is declared to be in
also identifies the specific written form of that language used in that element,
known as the
content writing system
Depending on the
document language
's facilities for identifying the
content language
this information can be explicit or implied.
See the normative
Appendix F.
Identifying the Content Writing System
Note:
Some languages have more than one writing system tradition;
in other cases a language can be transliterated into a foreign writing system.
Authors should
subtag
such cases
so that the UA can adapt appropriately.
1.4.
Characters and Letters
The basic unit of typesetting is the
character
However, because writing systems are not always as simple as the basic English alphabet,
what a
character
actually is depends on the context in which the term is used.
For example, in Hangul (the Korean writing system),
each square representation of a syllable
(e.g.
Han
can be considered a
character
However, the square symbol is really composed of multiple letters each representing a phoneme
(e.g.
and these also could each be considered a
character
A basic unit of computer text encoding, for any given encoding,
is also called a
character
and depending on the encoding,
a single encoding
character
might correspond
to the entire pre-composed syllabic
character
(e.g.
),
to the individual phonemic
character
(e.g.
),
or to smaller units such as
a base letterform (e.g.
and any combining marks that vary it (e.g. extra strokes that represent aspiration).
In turn, a single encoding
character
can be represented in the data stream as one or more bytes;
and in programming environments one byte is sometimes also called a
character
Therefore the term
character
is fairly ambiguous where technical precision is required.
For text layout, we will refer to the
typographic character unit
as the basic unit of text.
Even within the realm of text layout,
the relevant
character
unit depends on the operation.
For example, line-breaking and letter-spacing will segment
a sequence of Thai characters that include U+0E33 THAI CHARACTER SARA AM differently;
or the behaviour of a conjunct consonant in a script such as Devanagari
may depend on the font in use.
So the
typographic character
represents a unit of the writing system—
such as a Latin alphabetic letter (including its diacritics),
Hangul syllable,
Chinese ideographic character,
Myanmar syllable cluster—
that is indivisible with respect to a particular typographic operation
(line-breaking, first-letter effects, tracking, justification, vertical arrangement, etc.).
Unicode Standard Annex #29: Text Segmentation
defines a unit called the
grapheme cluster
which approximates the
typographic character
A UA must use the
extended grapheme cluster
(not
legacy grapheme cluster
), as defined in
[UAX29]
as the basis for its
typographic character unit
However, the UA should tailor the definitions
as required by typographic tradition
since the default rules are not always appropriate or ideal—
and is expected to tailor them differently
depending on the operation as needed.
Note: The rules for such tailorings are out of scope for CSS.
The following are some examples of
typographic character unit
tailorings
required by standard typesetting practice:
In some scripts such as Myanmar or Devanagari,
the
typographic character unit
for both justification and line-breaking
is an entire syllable,
which can include more than one
[UAX29]
grapheme cluster
In other scripts such as Thai or Lao,
even though for line-breaking the
typographic character
matches Unicode’s default
grapheme clusters
for letter-spacing the relevant unit
is
less
than a
[UAX29]
grapheme cluster
and may require decomposition or other substitutions
before spacing can be inserted.
For instance,
to properly letter-space the Thai word คำ (U+0E04 + U+0E33),
the U+0E33 needs to be decomposed into U+0E4D + U+0E32,
and then the extra letter-space inserted before the U+0E32: คํ า.
A slightly more complex example is น้ำ (U+0E19 + U+0E49 + U+0E33).
In this case, normal Thai shaping will first decompose the U+0E33 into U+0E4D + U+0E32
and then swap the U+0E4D with the U+0E49, giving U+0E19 + U+0E4D + U+0E49 + U+0E32.
As before the extra letter-space is then inserted before the U+0E32: นํ้ า.
Vertical typesetting
[CSS-WRITING-MODES-3]
can also require tailoring.
For example, when typesetting
upright
text,
Tibetan tsek and shad marks are kept with the preceding grapheme cluster,
rather than treated as an independent
typographic character unit
typographic letter unit
or
letter
for the purpose of this specification
is a
typographic character unit
belonging to one of the Letter or Number general
categories in Unicode.
[UAX44]
See
Character Properties
for how to determine the Unicode properties of a
typographic character unit
The rendering characteristics of a
typographic character unit
divided
by an element boundary is undefined.
Ideally each component should be rendered
according to the formatting requirements of its respective element’s properties
while maintaining correct shaping and positioning
of the
typographic character unit
as a whole.
However, depending on the nature of the formatting differences between its parts
and the capabilities of the font technology in use,
this is not always possible.
Therefore such a
typographic character unit
may be rendered as belonging to either side of the boundary,
or as some approximation of belonging to both.
Authors are forewarned that dividing
grapheme clusters
or ligatures
by element boundaries may give inconsistent or undesired results.
1.5.
Text Processing
CSS is built on
[UNICODE]
UAs that support Unicode must adhere to all normative requirements
of the Unicode Core Standard,
except where explicitly overridden by CSS.
UAs that use a different encoding are not explicitly supported by the CSS specifications;
they are, however, expected to fulfill the same text handling requirements
by assuming an appropriate mapping between that encoding and Unicode.
For the purpose of determining adjacency for text processing
(such as white space processing, text transformation, line-breaking, etc.),
and thus in general within this specification,
intervening
inline box
boundaries and
out-of-flow
elements
must be ignored.
With respect to text shaping, however, see
§ 7.3 Shaping Across Element Boundaries
2.
Transforming Text
2.1.
Case Transforms: the
text-transform
property
Name:
text-transform
Value:
none
[capitalize
uppercase
lowercase ]
||
full-width
||
full-size-kana
Initial:
none
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property transforms text for styling purposes.
It has no effect on the underlying content,
and must not affect the content of a plain text copy & paste operation.
Note:
The
text-transform
property only affects the presentation layer;
correct casing for semantic purposes is expected to be represented
in the source document.
Values have the following meanings:
none
No effects.
capitalize
Puts the first
typographic letter unit
of each word, if lowercase, in titlecase;
other characters are unaffected.
uppercase
Puts all
letters
in uppercase.
lowercase
Puts all
letters
in lowercase.
full-width
Puts all
typographic character units
in fullwidth form.
If a character does not have a corresponding fullwidth form,
it is left as is.
This value is typically used to typeset Latin letters and digits
as if they were ideographic characters.
full-size-kana
Converts all
small Kana
characters to the equivalent
full-size Kana
This value is typically used for ruby annotation text,
where authors may want all small Kana to be drawn as large Kana
to compensate for legibility issues at the small font sizes typically used in ruby.
The following example converts the ASCII characters
used in abbreviations in Japanese text to their fullwidth variants
so that they lay out and line break like ideographs:
abbr:lang(ja) { text-transform: full-width; }
Note:
The purpose of
text-transform
is
to allow for presentational casing transformations
without affecting the semantics of the document.
Note in particular that
text-transform
casing operations are lossy,
and can distort the meaning of a text.
While accessiblity interfaces may wish to convey
the apparent casing of the rendered text to the user,
the transformed text cannot be relied on to accurately represent
the underlying meaning of the document.
In this example,
the first line of text is capitalized as a visual effect.
section > p:first-of-type::first-line
text-transform
uppercase
This effect cannot be written into the source document
because the position of the line break depends on layout.
But also, the capitalization is not reflecting a semantic distinction
and is not intended to affect the paragraph’s reading;
therefore it belongs in the presentation layer.
In this example,
the
ruby
annotations,
which are half the size of the main paragraph text,
are transformed to use regular-size kana
in place of
small kana
rt
font-size
50
text-transform
full-size-kana
:is
h1
h2
h3
h4
rt
text-transform
none
/* unset for large text*/
Note that while this makes such letters easier to see at small type sizes,
the transformation distorts the text:
the reader needs to mentally substitute
small kana
in the appropriate places—
not unlike reading a text in English
with all “s” characters substituted by “f”.
2.1.1.
Mapping Rules
For
capitalize
, what constitutes a “word“ is UA-dependent;
[UAX29]
is suggested (but not required)
for determining such word boundaries.
Authors should not expect
capitalize
to follow
language-specific titlecasing conventions
(such as skipping articles in English).
Out-of-flow elements and inline element boundaries
must not introduce a
text-transform
word boundary
and must be ignored when determining such word boundaries.
The UA must use the full case mappings for Unicode
characters, including any conditional casing rules, as defined in
Default Case Algorithm section of The Unicode Standard
[UNICODE]
If (and only if) the
content language
of the element is, according to the rules of the
document language
known,
then any appropriate language-specific rules must be applied as well.
These minimally include, but are not limited to, the language-specific
rules in Unicode’s
SpecialCasing.txt
For example, in Turkish there are two “i”s, one with
a dot—“İ” and “i”— and one
without—“I” and “ı”. Thus the usual
case mappings between “I” and “i” are
replaced with a different set of mappings to their respective
undotted/dotted counterparts, which do not exist in English. This
mapping must only take effect if the
content language
is Turkish
written in its modern Latin-based
writing system
(or another Turkic language that uses Turkish casing rules);
in other languages, the usual mapping of “I”
and “i” is required. This rule is thus conditionally
defined in Unicode’s SpecialCasing.txt file.
The definition of fullwidth and halfwidth forms can be found on the
Unicode consortium web site at
[UAX11]
The mapping to fullwidth form is defined by taking code points with
the

or the

tag
in their
Decomposition_Mapping
in
[UAX44]
For the

tag,
the mapping is from the code point to the decomposition (minus

tag),
and for the

tag,
the mapping is from the decomposition (minus the

tag)
back to the original code point.
The mappings for small Kana to full-size Kana are defined in
Appendix G.
Small Kana Mappings
2.1.2.
Order of Operations
When multiple values are specified and therefore multiple transformations need to be applied,
they are applied in the following order:
capitalize
uppercase
, and
lowercase
full-width
full-size-kana
Text transformation happens after
§ 4.1.1 Phase I: Collapsing and Transformation
but before
§ 4.1.2 Phase II: Trimming and Positioning
This means that
full-width
only transforms
U+0020 spaces to U+3000 within
preserved
white space
Note: As defined in
Text Processing Order of Operations
transforming text affects line-breaking and other formatting operations.
3.
White Space and Wrapping: the
white-space
property
Name:
white-space
Value:
normal
pre
nowrap
pre-wrap
break-spaces
pre-line
Initial:
normal
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property specifies two things:
whether and how
white space
is collapsed
whether lines may
wrap
at unforced
soft wrap opportunities
Values have the following meanings, which must be interpreted
according to
the
White Space Processing
and
Line Breaking
rules:
normal
This value directs user agents to collapse sequences of
white space
into a single character (or
in some
cases
, no character).
Lines may wrap at allowed
soft wrap opportunities
as determined by the line-breaking rules in effect,
in order to minimize inline-axis overflow.
pre
This value prevents user agents from collapsing sequences of
white space
Segment breaks
such as line feeds
are preserved as
forced line breaks
Lines only break at
forced line breaks
content that does not fit within the block container overflows it.
nowrap
Like
normal
, this value collapses
white space
but like
pre
, it does not allow wrapping.
pre-wrap
Like
pre
, this value preserves
white space
but like
normal
, it allows wrapping.
break-spaces
The behavior is identical to that of
pre-wrap
except that:
Any sequence of
preserved
white space
or
other space separators
always takes up space,
including at the end of the line.
A line breaking opportunity exists after every
preserved
white space
character
and after every
other space separator
(including between adjacent spaces).
Note: This value does not guarantee that there will never be any overflow due to white space:
for example, if the line length is so short that even a single white space character does not fit,
overflow is unavoidable.
pre-line
Like
normal
, this value collapses consecutive
white space characters
and allows wrapping,
but preserves
segment breaks
in the source as
forced line breaks
White space
that was not removed or collapsed due to white space processing
is called
preserved white space
Note:
In some cases,
preserved white space
and
other space separators
can
hang
when at the end of the line;
this can affect whether they are measured for
intrinsic sizing
The following informative table summarizes the behavior of various
white-space
values:
New Lines
Spaces and Tabs
Text Wrapping
End-of-line
spaces
End-of-line
other space separators
normal
Collapse
Collapse
Wrap
Remove
Hang
pre
Preserve
Preserve
No wrap
Preserve
No wrap
nowrap
Collapse
Collapse
No wrap
Remove
Hang
pre-wrap
Preserve
Preserve
Wrap
Hang
Hang
break-spaces
Preserve
Preserve
Wrap
Wrap
Wrap
pre-line
Preserve
Collapse
Wrap
Remove
Hang
See
White Space Processing Rules
for details on how
white space
collapses. An informative summary of
collapsing (
normal
and
nowrap
) is presented below:
A sequence of segment breaks and other
white space
between two
Chinese, Japanese, or Yi characters collapses into nothing.
A zero width space before or after a
white space
sequence
containing a segment break causes the entire sequence of
white space
to collapse into a zero width space.
Otherwise, consecutive
white space
collapses into a single
space
See
Line Breaking
for details on wrapping behavior.
4.
White Space Processing & Control Characters
The source text of a document often contains formatting
that is not relevant to the final rendering: for example,
breaking the source into segments
(lines) for ease of editing
or adding
white space characters
such as
tabs
and
spaces
to indent the source code.
CSS white space processing allows the author to control interpretation of such formatting:
to preserve or collapse it away when rendering the document.
White space processing in CSS
(which is controlled with the
white-space
property)
interprets
white space characters
only for rendering:
it has no effect on the underlying document data.
Note:
Depending on the document language,
segments can be separated by a particular newline sequence
(such as a line feed or CRLF pair),
or delimited by some other mechanism,
such as the SGML
RECORD-START
and
RECORD-END
tokens.
For CSS processing, each document language–defined “segment break” or “newline sequence”—
or if none are defined, each line feed (U+000A)—
in the text is treated as a
segment break
which is then interpreted for rendering as specified by the
white-space
property.
In the case of
[HTML]
each
newline sequence is normalized
to a single line feed (U+000A)
for representation in the DOM,
so when an HTML document is represented as a
[DOM]
tree
each line feed (U+000A)
is treated as as a
segment break
Note:
In most common CSS implementations,
HTML does not get styled directly.
Instead, it is processed into a
[DOM]
tree,
which is then styled.
Unlike HTML,
the DOM does not give any particular meaning to carriage returns (U+000D),
so they are not treated as
segment breaks
If carriage returns (U+000D) are inserted into the DOM
by means other than HTML parsing,
they then get treated as defined below.
Note: A document parser might
not only normalize any
segment breaks
but also collapse other space characters or
otherwise process white space according to markup rules.
Because CSS processing occurs
after
the parsing stage,
it is not possible to restore these characters for styling.
Therefore, some of the behavior specified below
can be affected by these limitations and
may be user agent dependent.
Note: Anonymous blocks consisting entirely of
collapsible
white space
are removed from the rendering tree.
Thus any such
white space
surrounding a block-level element is collapsed away.
See
[CSS2]
section
9.2.2.1
Control characters (
Unicode category
Cc
)—
other than tabs (U+0009),
line feeds (U+000A),
carriage returns (U+000D)
and sequences that form a
segment break
must be rendered as a visible glyph
which the UA must synthethize if the glyphs found in the font are not visible,
and must be otherwise treated as any other character
of the Other Symbols (
So
general category
and Common
script
The UA may use a glyph provided by a font specifically for the control character,
substitute the glyphs provided for the corresponding symbol in the Control Pictures block,
generate a visual representation of its code point value,
or use some other method to provide an appropriate visible glyph.
As required by
[UNICODE]
unsupported
Default_ignorable
characters
must be ignored for text rendering.
Carriage returns (U+000D) are treated identically to spaces (U+0020) in all respects.
Note:
For HTML documents,
carriage returns present in the source code
are converted to line feeds at the parsing stage
(see
HTML 5 §13.2.3.5 Preprocessing the input stream
and the definition of
normalize newlines
in
[INFRA]
and therefore do no appear as U+000D to CSS.
However, the character
is
preserved—
and the above rule observable—
when encoded using an escape sequence (

).
4.1.
The White Space Processing Rules
Except where specified otherwise,
white space processing in CSS affects only
the
document white space characters
spaces
(U+0020),
tabs
(U+0009), and
segment breaks
Note: The set of characters considered
document white space
(part of the document content)
and those considered syntactic white space (part of the CSS syntax)
are not necessarily identical.
However, since both include spaces (U+0020), tabs (U+0009), and line feeds (U+000A)
most authors won’t notice any differences.
Besides
Space (U+0020)
and No-Break Space (U+00A0),
Unicode
[UNICODE]
defines a number of additional space separator characters.
In this specification
all characters in the Unicode Zs category (See
[UAX44]
except Space (U+0020)
and No-Break Space (U+00A0)
are collectively referred to as
other space separators
4.1.1.
Phase I: Collapsing and Transformation
For each inline (including anonymous inlines;
see
[CSS2]
section
9.2.2.1
within an
inline formatting context
white space characters
are processed as follows
prior to
line breaking
and
bidi reordering
ignoring
bidi formatting characters
(characters with the
Bidi_Control
property
[UAX9]
as if they were not there:
If
white-space
is set to
normal
nowrap
, or
pre-line
white space characters
are considered
collapsible
and are processed by performing the following steps:
Any sequence of collapsible
spaces
and
tabs
immediately preceding or following a
segment break
is removed.
Collapsible
segment breaks
are transformed for
rendering according to the
segment break transformation rules
Every
collapsible
tab
is converted to a collapsible space (U+0020).
Any
collapsible
space
immediately following another
collapsible
space
—even
one outside the boundary of the inline containing that
space
provided both
spaces
are within the same inline formatting
context—is collapsed to have zero advance width. (It is
invisible, but retains its
soft wrap opportunity
, if any.)
If
white-space
is set to
pre
pre-wrap
, or
break-spaces
any sequence of spaces is treated as a sequence of non-breaking spaces.
However, for
pre-wrap
soft wrap opportunity
exists at the end of a sequence of
spaces
and/or
tabs
while for
break-spaces
soft wrap opportunity
exists after every
space
and every
tab
The following example illustrates
the interaction of white-space collapsing and bidirectionality.
Consider the following markup fragment, taking special note of
spaces
(with varied backgrounds and borders for emphasis and identification):
A


C
where the

element represents a left-to-right embedding
and the

element represents a right-to-left embedding.
If the
white-space
property is set to
normal
the white-space processing model will result in the following:
The
space
before the B (
will collapse with the
space
after the A (
).
The
space
before the C (
will collapse with the
space
after the B (
).
This will leave two
spaces
one after the A in the left-to-right embedding level,
and one after the B in the right-to-left embedding level.
The text will then be ordered according to the Unicode bidirectional algorithm,
with the end result being:
BC
Note that there will be two
spaces
between A and B,
and none between B and C.
This is best avoided by putting
spaces
outside the element
instead of just inside the opening and closing tags and, where practical,
by relying on implicit bidirectionality instead of explicit embedding levels.
4.1.2.
Phase II: Trimming and Positioning
Then, the entire block is rendered.
Inlines are laid out,
taking
bidi reordering
into account,
and
wrapping
as specified by the
white-space
property.
As each line is laid out,
A sequence of
collapsible
spaces
at the beginning of a line
is removed.
If the
tab size
is zero,
preserved
tabs
are not rendered.
Otherwise, each
preserved
tab
is rendered as a horizontal shift
that lines up the start edge of the next glyph with the next
tab stop
If this distance is less than 0.5
ch
then the subsequent
tab stop
is used instead.
Tab stops
occur at points that are multiples of the
tab size
from the starting content edge
of the
preserved
tab
's nearest
block container
ancestor.
The
tab size
is given by the
tab-size
property.
Note:
See
[UAX9]
for
rules on how U+0009 tabulation interacts with bidi
A sequence at the end of a line
of
collapsible
spaces
is removed,
as well as any trailing U+1680 OGHAM SPACE MARK
whose
white-space
property is
normal
nowrap
, or
pre-line
Note:
Due to
[UAX9]
rule
L1
a sequence of
collapsible
spaces
located at the end of the line
prior to
bidi reordering
[CSS-WRITING-MODES-3]
will also be at the end of the line after reordering.
If there remains any sequence of
white space
and/or
other space separators
at the end of a line (after
bidi reordering
[CSS-WRITING-MODES-3]
):
If
white-space
is set to
normal
nowrap
, or
pre-line
the UA must
hang
this sequence (unconditionally).
If
white-space
is set to
pre-wrap
the UA must (unconditionally)
hang
this sequence,
unless the sequence is followed by a
forced line break
in which case it must
conditionally hang
the sequence is instead.
It may also visually collapse the character advance widths
of any that would otherwise overflow.
Note:
Hanging
the white space rather than collapsing it
allows users to see the space when selecting or editing text.
If
white-space
is set to
break-spaces
spaces
tabs
, and
other space separators
are treated the same as other visible characters:
they cannot
hang
nor have their advance width collapsed.
Note:
Such characters therefore take up space,
and depending on the available space
and applicable line breaking controls
will either overflow or cause the line to wrap.
This example shows that
conditionally hanging
white space
at the end of lines with forced breaks
provides symmetry with the start of the line.
An underline is added to help visualize the spaces.
white-space
pre-wrap
width
ch
border
solid
px
font-family
monospace
text-align
center
The sample above would be rendered as follows:
Since the final
space
is before a forced line break
and does not overflow,
it does not hang,
and centering works as expected.
This example illustrates the difference
between
hanging
spaces
at the end of lines without forced breaks,
and
conditionally hanging
them at the end of lines with forced breaks.
An underline is added to help visualize the
spaces
white-space
pre-wrap
width
ch
border
solid
px
font-family
monospace
0 0 0 0
The sample above would be rendered as follows:
0 0
If
text-align
right
was added,
the result would be as follows:
0 0
As the
preserved
spaces
at the end of lines without a forced break must
hang
they are not considered when placing the rest of the line during text alignment.
When aligning towards the end,
this means any such
spaces
will overflow,
and will not prevent the rest of the line’s content from being flush with the edge of the line.
On the other hand,
preserved spaces at the end of a line
with
a forced break
conditionally hang
Since the space at the end of the last line would not overflow in this example,
it does not
hang
and therefore is considered during text alignment.
In the following example,
there is not enough room on any line to fit the end-of-line spaces,
so they
hang
on all lines:
the one on the line without a forced break because it must,
as well as the one on the line with a forced break,
because it
conditionally hangs
and overflows.
An underline is added to help visualize the spaces.
white-space
pre-wrap
width
ch
border
solid
px
font-family
monospace
0 0 0 0
0 0
0 0
The last line is not wrapped before the last
because characters that
conditionally hang
are not considered
when measuring the line’s contents for fit.
4.1.3.
Segment Break Transformation Rules
When
white-space
is
pre
pre-wrap
break-spaces
, or
pre-line
segment breaks
are not
collapsible
and are instead transformed into a preserved line feed (U+000A).
For other values of
white-space
segment breaks
are
collapsible
and are collapsed as follows:
First, any collapsible
segment break
immediately following another collapsible
segment break
is removed.
Then any remaining
segment break
is
either transformed into a space (U+0020) or removed
depending on the context before and after the break.
The rules for this operation are UA-defined in this level.
Note:
The white space processing rules have already
removed any
tabs
and
spaces
around the
segment break
before this context is evaluated.
The purpose of the segment break transformation rules
(and white space collapsing in general)
is to “unbreak” text that has been
broken into segments
to make the document source code easier to work with.
In languages that use word separators, such as English and Korean,
“unbreaking” a line requires joining the two lines with a
space
Here is an English paragraph
that is broken into multiple lines
in the source code so that it can
be more easily read and edited
in a text editor.
Here is an English paragraph that is broken into multiple lines in the source code so that it can be more easily read and edited in a text editor.
Eliminating a line break in English requires maintaining a
space
in its place.
In languages that have no word separators, such as Chinese,
“unbreaking” a line requires joining the two lines with no intervening space.
這個段落是那麼長，
在一行寫不行。最好
用三行寫。
這個段落是那麼長，在一行寫不行。最好用三行寫。
Eliminating a line break in Chinese requires eliminating any intervening
white space
The segment break transformation rules can use adjacent context
to either transform the segment break into a space
or eliminate it entirely.
Note:
Historically, HTML and CSS have unconditionally converted
segment breaks
to spaces,
which has prevented content authored in languages such as Chinese
from being able to break lines within the source.
Thus UA heurstics need to be conservative about where they discard
segment breaks
even as they strive to improve support for such languages.
4.2.
Tab Character Size: the
tab-size
property
Name:
tab-size
Value:


Initial:
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
the specified number or absolute length
Canonical order:
n/a
Animation type:
by computed value type
This property determines the
tab size
used to render
preserved
tab characters (U+0009).

represents the measure as a multiple of the advance width of the space character (U+0020)
of the nearest
block container
ancestor of the
preserved
tab
including its associated
letter-spacing
and
word-spacing
Negative values are not allowed.
5.
Line Breaking and Word Boundaries
When inline-level content is laid out into lines, it is broken across line boxes.
Such a break is called a
line break
When a line is broken due to explicit line-breaking controls
(such as a
preserved
newline character),
or due to the start or end of a block,
it is a
forced line break
When a line is broken due to content
wrapping
(i.e. when the UA creates unforced line breaks in order to fit the content within the measure),
it is a
soft wrap break
The process of breaking inline-level content into lines is called
line breaking
Wrapping is only performed at an allowed break point,
called a
soft wrap opportunity
When wrapping is enabled (see
white-space
),
the UA must minimize the amount of content overflowing a line
by wrapping the line at a
soft wrap opportunity
if one exists.
In most writing systems,
in the absence of hyphenation a
soft wrap opportunity
occurs only at word boundaries.
Many such systems use
spaces
or punctuation to explicitly separate words,
and
soft wrap opportunities
can be identified by these characters.
Scripts such as Thai, Lao, and Khmer, however,
do not use spaces or punctuation to separate words.
Although the zero width space (U+200B) can be used as an explicit word delimiter in these scripts,
this practice is not common.
As a result, a lexical resource is needed to correctly identify
soft wrap opportunities
in such texts.
In some other writing systems,
soft wrap opportunities
are based on orthographic syllable boundaries,
not word boundaries.
Some of these systems, such as Javanese and Balinese,
are similar to Thai and Lao in that they
require analysis of the text to find breaking opportunities.
In others such as Chinese (as well as Japanese, Yi, and sometimes also Korean),
each syllable tends to correspond to a single
typographic letter unit
and thus line breaking conventions allow the line to break
anywhere
except
between certain character combinations.
Additionally the level of strictness in these restrictions
varies with the typesetting style.
While CSS does not fully define where
soft wrap opportunities
occur,
some controls are provided to distinguish common variations:
The
line-break
property allows choosing various levels of “strictness”
for line breaking restrictions.
The
word-break
property controls what types of letters
are glommed together to form unbreakable “words”,
causing CJK characters to behave like non-CJK text or vice versa.
The
hyphens
property controls whether automatic hyphenation
is allowed to break words in scripts that hyphenate.
The
overflow-wrap
property allows the UA to take a break anywhere
in otherwise-unbreakable strings that would otherwise overflow.
Note:
[UAX14]
defines a baseline behavior
for line breaking for all scripts in Unicode,
which is expected to be further tailored.
More information on line breaking conventions
can be found in
[JLREQ]
and
[JIS4051]
for Japanese,
[CLREQ]
and
[ZHMARK]
for Chinese.
See also the
Internationalization Working Group
’s
Typography Index
[TYPOGRAPHY]
which includes more information on additional languages.
Any guidance on additional appropriate references
would be much appreciated.
5.1.
Line Breaking Details
When determining
line breaks
The interaction of
line breaking
and bidirectional text is defined by
[CSS-WRITING-MODES-3]
and
[UAX9]
see in particular
CSS Writing Modes 3 §2.4 Applying the Bidirectional Reordering Algorithm
and
UAX9§3.4 Reordering Resolved Levels
Regardless of the
white-space
value,
lines always break at each
preserved
forced break character:
thus
for all values, line-breaking behavior defined for
the
BK
and
NL
Unicode line breaking classes
[UAX14]
must be honored.
Note:
The bidi implications of such
forced line breaks
are defined by
[UAX9]
Except where explicitly defined otherwise
(e.g. for
line-break: anywhere
or
overflow-wrap: anywhere
line breaking behavior defined for
the
WJ
ZW
GL
, and
ZWJ
Unicode line breaking classes
[UAX14]
must be honored.
UAs that allow wrapping at punctuation
other than
word separators
in writing systems that use them
should
prioritize breakpoints.
(For example, if breaks after slashes are given a lower priority than spaces,
the sequence “check /etc” will never break between the "/" and the "e".)
As long as care is taken to avoid such awkward breaks,
allowing breaks at appropriate punctuation other than
word separators
is recommended,
as it results in more even-looking margins, particularly in narrow measures.
The UA may use the width of the containing block, the text’s language,
the
line-break
value,
and other factors in assigning priorities:
CSS does not define prioritization of line breaking opportunities.
Prioritization of
word separators
is not expected,
however,
if
word-break: break-all
is specified
(since this value explicitly requests line breaking behavior
not based on breaking at
word separators
)—
and is forbidden under
line-break: anywhere
Out-of-flow elements
and inline element boundaries
do not introduce a
forced line break
or
soft wrap opportunity
in the flow.
For Web-compatibility
there is a
soft wrap opportunity
before and after each replaced element or other
atomic inline
even when adjacent to a character that would normally suppress them,
such as U+00A0 NO-BREAK SPACE.
For
soft wrap opportunities
created by characters that disappear at the line break (e.g. U+0020 SPACE),
properties on the box directly containing that character control the line breaking at that opportunity.
For
soft wrap opportunities
defined by the boundary between two characters,
the
white-space
property on the nearest common ancestor of the two characters controls breaking;
which elements’
line-break
word-break
, and
overflow-wrap
properties
control the determination of
soft wrap opportunities
at such boundaries
is undefined in Level 3.
For
soft wrap opportunities
before the first or after the last character of a box,
the break occurs immediately before/after the box (at its margin edge)
rather than breaking the box between its content edge and the content.
Line breaking in/around Ruby is defined in
CSS Ruby
[CSS-RUBY-1]
In order to avoid unexpected overflow,
if the User Agent is unable to perform the requisite lexical or orthographic analysis
for line breaking any
content language
that requires it—
for example due to lacking a dictionary for certain languages—
it must assume a
soft wrap opportunity
between pairs of
typographic letter units
in that writing system.
Note:
This provision is not triggered merely when
the UA fails to find a word boundary in a particular text run;
the text run may well be a single unbreakable word.
It applies for example
when a text run is composed of Khmer characters (U+1780 to U+17FF)
if the User Agent does not know how to determine
word boundaries in Khmer.
5.2.
Breaking Rules for Letters: the
word-break
property
Name:
word-break
Value:
normal
keep-all
break-all
break-word
Initial:
normal
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property specifies
soft wrap opportunities
between letters,
i.e. where it is “normal” and permissible to break lines of text.
Specifically it controls whether a
soft wrap opportunity
generally exists
between adjacent
typographic letter units
treating non-
letter
typographic character units
belonging to the
NU
AL
AI
, or
ID
Unicode line breaking classes
[UAX14]
as
typographic letter units
for this purpose (only).
It does not affect rules governing the
soft wrap opportunities
created by
white space
(as well as by
other space separators
) and around punctuation.
(See
line-break
for controls affecting punctuation and small kana.)
For example, in some styles of CJK typesetting, English words are allowed
to break between any two letters, rather than only at spaces or hyphenation points;
this can be enabled with
word-break:break-all
An example of English text embedded in Japanese
being broken at an arbitrary point in the word.
As another example, Korean has two styles of line-breaking:
between any two Korean syllables (
word-break: normal
or, like English, mainly at spaces (
word-break: keep-all
).
각 줄의 마지막에 한글이 올 때 줄 나눔
준을
“글자” 또는 “어절” 단위로 한다.
각 줄의 마지막에 한글이 올 때 줄 나눔
기준을
“글자” 또는 “어절” 단위로 한다.
Ethiopic similarly has two styles of line-breaking,
either only breaking at
word separators
word-break: normal
),
or also allowing breaks between letters within a word (
word-break: break-all
).
ተወልዱ፡ኵሉ፡ሰብእ፡ግዑዛን፡ወዕሩያን፡
በማዕረግ
፡ወብሕግ።ቦሙ፡ኅሊና፡ወዐቅል፡
ወይትጌበሩ፡አሐዱ፡ምስለ፡አሀዱ፡
በመንፈሰ፡እኍና።
ተወልዱ፡ኵሉ፡ሰብእ፡ግዑዛን፡ወዕሩያን፡
በማ
ዕረግ
፡ወብሕግ።ቦሙ፡ኅሊና፡ወዐቅል፡ወይትጌ
በሩ፡አሐዱ፡ምስለ፡አሀዱ፡በመንፈሰ፡እኍና።
Note: To enable additional break opportunities only in the case of overflow,
see
overflow-wrap
Values have the following meanings:
normal
Words break according to their customary rules,
as described
above
Korean, which commonly exhibits two different behaviors,
allows breaks between any two consecutive Hangul/Hanja.
For Ethiopic, which also exhibits two different behaviors,
such breaks within words are not allowed.
break-all
Breaking is allowed within “words”:
specifically,
in addition to
soft wrap opportunities
allowed for
normal
any
typographic letter units
(and any
typographic character units
resolving to the
NU
(“numeric”),
AL
(“alphabetic”), or
SA
(“Southeast Asian”)
line breaking classes
[UAX14]
are instead treated as
ID
(“ideographic characters”)
for the purpose of line-breaking.
Hyphenation is not applied.
Note:
This value does not affect
whether there are
soft wrap opportunities
around punctuation characters.
To allow breaks anywhere, see
line-break: anywhere
Note:
This option enables the other common behavior for Ethiopic.
It is also often used in a context where
the text consists predominantly of CJK characters
with only short non-CJK excerpts,
and it is desired that the text be better distributed on each line.
keep-all
Breaking is forbidden within “words”:
implicit
soft wrap opportunities
between
typographic letter units
(or other
typographic character units
belonging to the
NU
AL
AI
, or
ID
Unicode line breaking classes
[UAX14]
are suppressed,
i.e. breaks are prohibited between pairs of such characters
(regardless of
line-break
settings other than
anywhere
except where opportunities exist due to dictionary-based breaking.
Otherwise this option is equivalent to
normal
In this style, sequences of CJK characters do not break.
Note: This is the other common behavior for Korean (which uses
spaces
between words),
and is also useful for mixed-script text where CJK snippets are mixed
into another language that uses
spaces
for separation.
Symbols that line-break the same way as letters of a particular category
are affected the same way as those letters.
Here’s a mixed-script sample text:
这是一些汉字 and some Latin
و کمی خط عربی
และตัวอย่างการเขียนภาษาไทย በጽሑፍ፡ማራዘሙን፡አንዳንድ፡
The break-points are determined as follows (indicated by ‘·’):
word-break: normal
这·是·一·些·汉·字·and·some·Latin·
و·کمی·خط·عربی
·และ·ตัวอย่าง·การเขียน·ภาษาไทย·በጽሑፍ፡·ማራዘሙን፡·አንዳንድ፡
word-break: break-all
这·是·一·些·汉·字·a·n·d·s·o·m·e·L·a·t·i·n·
و·ﮐ·ﻤ·ﻰ·ﺧ·ﻁ·ﻋ·ﺮ·ﺑ·ﻰ
·แ·ล·ะ·ตั·ว·อ·ย่·า·ง·ก·า·ร·เ·ขี·ย·น·ภ·า·ษ·า·ไ·ท·ย·በ·ጽ·ሑ·ፍ፡·ማ·ራ·ዘ·ሙ·ን፡·አ·ን·ዳ·ን·ድ፡
word-break: keep-all
这是一些汉字·and·some·Latin·
و·کمی·خط·عربی
·และ·ตัวอย่าง·การเขียน·ภาษาไทย·በጽሑፍ፡·ማራዘሙን፡·አንዳንድ፡
Japanese is usually typeset allowing line breaks within words.
However, it is sometimes preferred to suppress these wrapping opportunities
and to only allow wrapping at the end of certain sentence fragments.
This is most commonly done in very short pieces of text,
such as headings and table or figure captions.
This can be achieved by marking the allowed wrapping points
with
wbr
or U+200B ZERO WIDTH SPACE,
and suppressing the other ones using
word-break: keep-all
For instance, the following markup can produce either of the renderings below,
depending on the value of the
word-break
property:
h1
窓ぎわの
wbr
トットちゃん
h1
h1
word-break
normal
h1
word-break
keep-all
Expected rendering
窓ぎわのトットちゃ
窓ぎわの
トットちゃん
Result in your browser
窓ぎわの
トットちゃん
窓ぎわの
トットちゃん
When shaping scripts such as Arabic
are allowed to break within words due to
break-all
the characters must still be shaped
as if the word were
not broken
(see
§ 5.6 Shaping Across Intra-word Breaks
).
For compatibility with legacy content,
the
word-break
property also supports a deprecated
break-word
keyword.
When specified, this has the same effect as
word-break: normal
and
overflow-wrap: anywhere
regardless of the actual value of the
overflow-wrap
property.
5.3.
Line Breaking Strictness: the
line-break
property
Name:
line-break
Value:
auto
loose
normal
strict
anywhere
Initial:
auto
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property specifies the strictness of line-breaking rules applied
within an element:
especially how
wrapping
interacts with punctuation and symbols.
Values have the following meanings:
auto
The UA determines the set of line-breaking restrictions to use,
and it may vary the restrictions based on the length of the line; e.g.,
use a less restrictive set of line-break rules for short lines.
loose
Breaks text using the least restrictive set of line-breaking
rules. Typically used for short lines, such as in newspapers.
normal
Breaks text using the most common set of line-breaking rules.
strict
Breaks text using the most stringent set of line-breaking
rules.
anywhere
There is a
soft wrap opportunity
around every
typographic character unit
including around any punctuation character or
preserved white spaces
or in the middle of words,
disregarding any prohibition against line breaks,
even those introduced by characters with the GL, WJ, or ZWJ character class (see
[UAX14]
or mandated by the
word-break
property.
The different wrapping opportunities must not be prioritized.
Hyphenation is not applied.
Note:
This value triggers the line breaking rules typically seen in terminals.
Note:
anywhere
only allows
preserved white spaces
at the end of the line
to be wrapped to the next line when
white-space
is set to
break-spaces
because in other cases:
preserved white space
at the end/start of the line is discarded (
normal
pre-line
wrapping is forbidden altoghether (
nowrap
pre
the
preserved white space
hang
pre-wrap
).
When it does have an effect on
preserved white space
with
white-space: break-spaces
it allows breaking before the first space of a sequence,
which
break-spaces
on its own does not.
CSS distinguishes between four levels of strictness in the rules for
text wrapping.
The precise set of rules in effect for each of
loose
normal
, and
strict
is up to the UA
and should follow language conventions.
However, this specification does require that:
The following breaks are forbidden in
strict
line breaking
and allowed in
normal
and
loose
breaks before Japanese small kana or the Katakana-Hiragana prolonged sound mark,
i.e. character from the Unicode line breaking class
CJ
[UAX14]
The following breaks are allowed for
normal
and
loose
line breaking
if the
writing system
is
Chinese
or
Japanese
and are otherwise forbidden:
breaks before certain CJK hyphen-like characters:
〜 U+301C,
゠ U+30A0
The following breaks are allowed for
loose
line breaking
if the preceding character belongs to the Unicode line breaking class
ID
[UAX14]
(including when the preceding character is treated as
ID
due to
word-break: break-all
),
and are otherwise forbidden:
breaks before hyphens:
‐ U+2010, – U+2013
The following breaks are forbidden for
normal
and
strict
line breaking
and allowed in
loose
breaks before iteration marks:
々 U+3005, 〻 U+303B, ゝ U+309D,
ゞ U+309E, ヽ U+30FD, ヾ U+30FE
breaks between inseparable characters
(such as ‥ U+2025, … U+2026)
i.e. characters from the Unicode line breaking class
IN
[UAX14]
The following breaks are allowed for
loose
if the
writing system
is
Chinese
or
Japanese
and are otherwise forbidden:
breaks before certain centered punctuation marks:
・ U+30FB,
： U+FF1A, ； U+FF1B, ･ U+FF65,
‼ U+203C,
⁇ U+2047, ⁈ U+2048, ⁉ U+2049,
！ U+FF01, ？ U+FF1F
breaks before suffixes:
Characters with the Unicode line breaking class
PO
[UAX14]
and the
East Asian Width property
[UAX11]
Ambiguous
Fullwidth
, or
Wide
breaks after prefixes:
Characters with the Unicode line breaking class
PR
[UAX14]
and the
East Asian Width property
[UAX11]
Ambiguous
Fullwidth
, or
Wide
Note:
The requirements listed above
only create distinctions in CJK text.
In an implementation that matches only the rules above,
and no additional rules,
line-break
would only affect CJK code points
unless the writing system is tagged as
Chinese
or
Japanese
Future levels may add additional specific rules
for other writing systems and languages
as their requirements become known.
As UAs can add additional distinctions
between
strict
normal
loose
modes,
these values can exhibit differences in other writing systems as well.
For example, a UA with sufficiently-advanced Thai language processing ability
could choose to map different levels of strictness in Thai line-breaking
to these keywords,
e.g. disallowing breaks within compound words in
strict
mode
(e.g. breaking ตัวอย่างการเขียนภาษาไทย as ตัวอย่าง·การเขียน·ภาษาไทย)
while allowing more breaks in
loose
(ตัวอย่าง·การ·เขียน·ภาษา·ไทย).
Note: The CSSWG recognizes that in a future edition of the
specification finer control over line breaking may be necessary to
satisfy high-end publishing requirements.
5.4.
Hyphenation: the
hyphens
property
Hyphenation
is the controlled splitting of words
where they usually would not be allowed to break
to improve the layout of paragraphs,
typically splitting words at syllabic or morphemic boundaries,
and visually indicating the split (usually by inserting a hyphen, U+2010).
In some cases, hyphenation may also alter the spelling of a word.
Regardless, hyphenation is a rendering effect only:
it must have no effect on the underlying document content
or on text selection or searching.
Hyphenation occurs when the line breaks at a valid
hyphenation opportunity
which is a type of
soft wrap opportunity
that exists within a word where
hyphenation
is allowed.
In CSS
hyphenation opportunities
are controlled
with the
hyphens
property.
CSS Text Level 3 does not define the exact rules for
hyphenation
however UAs are strongly encouraged
to optimize their choice of break points
and to chose language-appropriate hyphenation points.
Note:
The
soft wrap opportunity
introduced by
the U+002D HYPHEN-MINUS character
or the U+2010 HYPHEN character
is not a
hyphenation opportunity
as no visual indication of the split is
created
when wrapping:
these characters are visible whether the line is wrapped at that point or not.
Hyphenation opportunities
are
considered when calculating
min-content intrinsic sizes
Name:
hyphens
Value:
none
manual
auto
Initial:
manual
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property controls whether
hyphenation
is allowed to create more
soft wrap opportunities
within a line of text.
Values have the following meanings:
none
Words are not hyphenated, even if characters inside
the word explicitly define
hyphenation opportunities
Note:
This does not suppress the existing
soft wrap opportunities
introduced by always visible characters such as
U+002D HYPHEN-MINUS
or U+2010 HYPHEN.
manual
Words are only hyphenated where there are characters inside the word
that explicitly suggest
hyphenation opportunities
In Unicode, U+00AD is a conditional "soft hyphen" and U+2010 is an
unconditional hyphen. Unicode Standard Annex #14 describes the
role of soft hyphens in
Unicode line breaking.
[UAX14]
In HTML, ­ represents the soft hyphen character,
which suggests a hyphenation opportunity.
ex­ample
auto
Words may be broken at
hyphenation opportunities
determined automatically by a language-appropriate hyphenation resource
in addition to those indicated explicitly by a conditional hyphen.
Automatic
hyphenation opportunities
within a word must be ignored
if the word contains a conditional hyphen (­ or U+00AD),
in favor of the conditional hyphen(s).
However, if, even after breaking at such opportunities,
a portion of that word is is still too long to fit on one line,
an automatic hyphenation opportunity may be used.
Correct automatic hyphenation requires a hyphenation resource
appropriate to the language of the text being broken.
The UA must therefore only automatically hyphenate text
for which the
content language
is known
and for which it has an appropriate hyphenation resource.
Authors should correctly tag their content’s
language
(e.g. using the HTML
lang
attribute
or XML
xml:lang
attribute)
in order to obtain correct automatic hyphenation.
The UA may use language-tailored heuristics
to exclude certain words
from automatic hyphenation.
For example, a UA might try to avoid hyphenation in proper nouns
by excluding words matching certain capitalization and punctuation patterns.
Such heuristics are not defined by this specification.
(Note that such heuristics will need to vary by language:
English and German, for example, have very different capitalization conventions.)
For the purpose of the
hyphens
property,
what constitutes a “word” is UA-dependent.
However, inline element boundaries
and out-of-flow elements
must be ignored when determining word boundaries.
Any glyph(s) shown due to hyphenation
at a
hyphenation opportunity
created by a conditional hyphen character (such as U+00AD SOFT HYPHEN)
are represented by that character
and are styled according to the properties applied to it.
When shaping scripts such as Arabic are allowed to break within words
due to hyphenation,
the characters must still be shaped
as if the word were
not broken
(see
§ 5.6 Shaping Across Intra-word Breaks
).
For example, if the Uyghur word “داميدى”
were hyphenated, it would appear as
not as
5.5.
Overflow Wrapping: the
overflow-wrap
word-wrap
property
Name:
overflow-wrap
word-wrap
Value:
normal
break-word
anywhere
Initial:
normal
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property specifies whether the UA may break at otherwise disallowed points within a line
to prevent overflow,
when an otherwise-unbreakable string is too long to fit within the line box.
It only has an effect when
white-space
allows
wrapping
. Possible values:
normal
Lines may break only at allowed break points. However, the restrictions
introduced by
word-break: keep-all
may be relaxed to match
word-break: normal
if there are no otherwise-acceptable break points in the line.
anywhere
An otherwise unbreakable sequence of
characters
may be broken at an arbitrary point if
there are no otherwise-acceptable break points in the line.
Shaping characters are still shaped as if the word were not
broken, and grapheme clusters must stay together as one unit.
No hyphenation character is inserted at the break point.
Soft wrap opportunities
introduced by
anywhere
are considered
when calculating
min-content intrinsic sizes
break-word
As for
anywhere
except that
soft wrap opportunities
introduced by
break-word
are
not
considered
when calculating
min-content intrinsic sizes
For legacy reasons, UAs must treat
word-wrap
as a
legacy name alias
of the
overflow-wrap
property.
5.6.
Shaping Across Intra-word Breaks
When shaping scripts such as Arabic
wrap
at unforced
soft wrap opportunities
within words
(such as when breaking due to
word-break: break-all
line-break: anywhere
overflow-wrap: break-word
overflow-wrap: anywhere
or when
hyphenating
the characters must still be shaped
(their joining forms chosen)
as if the word were still whole.
For example, if the word “نوشتن” is broken between the “ش” and “ت”,
the “ش” still takes its initial form (“ﺷ”), and the “ت” its medial form (“ﺘ”)—
forming as in “ﻧﻮﺷ | ﺘﻦ”, not as in “نوش | تن”.
6.
Alignment and Justification
Alignment and justification controls how inline content is distributed within a line box.
6.1.
Text Alignment: the
text-align
shorthand
Name:
text-align
Value:
start
end
left
right
center
justify
match-parent
justify-all
Initial:
start
Applies to:
block containers
Inherited:
yes
Percentages:
see individual properties
Computed value:
see individual properties
Animation type:
discrete
Canonical order:
n/a
This
shorthand property
sets the
text-align-all
and
text-align-last
properties
and describes how the inline-level content of a block
is aligned along the inline axis
if the content does not completely fill the line box.
Values other than
justify-all
or
match-parent
are assigned to
text-align-all
and reset
text-align-last
to
auto
Values have the following meanings:
start
Inline-level content is aligned to the
start
edge of the line box.
end
Inline-level content is aligned to the
end
edge of the line box.
left
Inline-level content is aligned to the
line left
edge of the line box.
(In vertical writing modes,
this will be either the physical top or bottom,
depending on
text-orientation
.)
[CSS-WRITING-MODES-3]
right
Inline-level content is aligned to the
line right
edge of the line box.
(In vertical writing modes,
this will be either the physical top or bottom,
depending on
text-orientation
.)
[CSS-WRITING-MODES-3]
center
Inline-level content is centered within the line box.
justify
Text is justified according to the method specified by the
text-justify
property,
in order to exactly fill the line box.
Unless otherwise specified by
text-align-last
the last line before a forced break or the end of the block is
start
-aligned.
justify-all
Sets both
text-align-all
and
text-align-last
to
justify
forcing the last line to justify as well.
match-parent
This value behaves the same as
inherit
(computes to its parent’s computed value)
except that an
inherited value
of
start
or
end
is interpreted against the parent’s
(or the
initial containing block
’s, if there is no parent)
direction
value
and results in a computed value of either
left
or
right
When specified on the
text-align
shorthand,
sets both
text-align-all
and
text-align-last
to
match-parent
A block of text is a stack of
line boxes
This property specifies how the inline-level boxes within each line box
align with respect to the start and end sides of the line box.
Alignment is not with respect to the
viewport
or containing block.
In the case of
justify
, the UA may stretch or shrink any inline boxes
by
adjusting
their text. (See
text-justify
.)
If an element’s
white space
is not
collapsible
then the UA is not required to adjust its text for the purpose of justification
and may instead treat the text as having no
justification opportunities
If the UA chooses to adjust the text, then it must ensure
that
tab stops
continue to line up as required by the
white space processing rules
If (after justification, if any) the inline contents of a line box are too long to fit within it,
then the contents are
start
-aligned:
any content that doesn’t fit overflows the line box’s
end
edge.
See
Bidirectionality and line boxes
for details on how to determine the
start
and
end
edges of a line box.
6.2.
Default Text Alignment: the
text-align-all
property
Name:
text-align-all
Value:
start
end
left
right
center
justify
match-parent
Initial:
start
Applies to:
block containers
Inherited:
yes
Percentages:
n/a
Computed value:
keyword as specified, except for
match-parent
which computes as defined above
Canonical order:
n/a
Animation type:
discrete
This longhand of the
text-align
shorthand property
specifies the inline alignment of all lines of inline content in the block container,
except for last lines overridden by a non-
auto
value of
text-align-last
See
text-align
for a full description of values.
Authors should use the
text-align
shorthand instead of this property.
6.3.
Last Line Alignment: the
text-align-last
property
Name:
text-align-last
Value:
auto
start
end
left
right
center
justify
match-parent
Initial:
auto
Applies to:
block containers
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property describes how the last line of a block or a line
right before a
forced line break
is aligned.
If
auto
is specified,
content on the affected line is aligned per
text-align-all
unless
text-align-all
is set to
justify
in which case it is start-aligned.
All other values are interpreted as described for
text-align
6.4.
Justification Method: the
text-justify
property
Name:
text-justify
Value:
auto
none
inter-word
inter-character
Initial:
auto
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword
Canonical order:
n/a
Animation type:
discrete
This property selects the justification method used when a line’s
alignment is set to
justify
(see
text-align
).
The property applies to inlines,
but is inherited from block containers to the root inline box containing their inline-level contents.
It takes the following values:
auto
The UA determines the justification algorithm to follow, based
on a balance between performance and adequate presentation quality.
Since justification rules vary by writing system and language,
UAs should, where possible, use a justification algorithm appropriate to the text.
For example, the UA could use by default a justification method that is a
simple universal compromise for all writing systems—such as
primarily expanding
word separators
and between CJK
typographic letter units
along with secondarily expanding between Southeast Asian
typographic letter units
Then, in cases where the
content language
of the paragraph is known,
it could choose a more language-tailored justification behavior
e.g. following
[JLREQ]
for Japanese,
using cursive elongation for Arabic,
using
inter-word
for German,
etc.
An example of cursively-justified Arabic text,
rendered by
Tasmeem
Like English, Arabic can be justified by adjusting the spacing between words,
but in most styles it can also be justified by calligraphically elongating or compressing the letterforms themselves.
In this example, the upper text is extended to fill the line by the use of elongated (kashida) forms and swash forms,
while the bottom line is compressed slightly by using a stacked combination for the characters between ت and م.
By employing traditional calligraphic techniques,
a typesetter can justify the line while preserving flow and color,
providing a very high quality justification effect.
However, this is by its nature a very script-specific effect.
Mixed-script text with
text-justify: auto
this interpretation uses a universal-compromise justification method,
expanding at spaces as well as between CJK and Southeast Asian letters.
This effectively uses inter-word + inter-ideograph spacing
for lines that have word-separators and/or CJK characters
and falls back to inter-cluster behavior for lines that don’t
or for which the space stretches too far.
none
Justification is disabled: there are no
justification opportunities
within the text.
Mixed-script text with
text-justify: none
Note: This value is intended for use in user stylesheets
to improve readability or for accessibility purposes.
inter-word
Justification adjusts spacing at
word separators
only
(effectively varying the used
word-spacing
on the line).
This behavior is typical for languages that separate words using spaces,
like English or Korean.
Mixed-script text with
text-justify: inter-word
inter-character
Justification adjusts spacing between each pair of adjacent
typographic character units
(effectively varying the used
letter-spacing
on the line).
This value is sometimes used in East Asian systems such as Japanese.
Mixed-script text with
text-justify: inter-character
For legacy reasons, UAs must also support the alternate keyword
distribute
with the exact same meaning and behavior.
Since optimal justification is language-sensitive,
authors should correctly language-tag their content for the best results.
Note:
The guidelines in this level of CSS do not describe a complete
justification algorithm. They are merely a minimum set of requirements
that a complete algorithm should meet. Limiting the set of requirements
gives UAs some latitude in choosing a justification algorithm that
meets their needs and desired balance of quality, speed, and complexity.
6.4.1.
Expanding and Compressing Text
When justifying text, the user agent takes the remaining space between
the ends of a line’s contents and the edges of its line box, and
distributes that space throughout its contents so that the contents
exactly fill the line box.
The user agent may alternatively distribute negative space,
putting more content on the line than would otherwise fit under normal spacing conditions.
justification opportunity
is
a point where the justification algorithm may alter spacing within the text.
A justification opportunity can be provided by a single
typographic character unit
(such as a
word separator
),
or by the juxtaposition of two
typographic character units
As with controls for
soft wrap opportunities
whether a
typographic character unit
provides a
justification opportunity
is controlled by the
text-justify
value of its parent;
similarly, whether a
justification opportunity
exists between two consecutive
typographic character units
is determined by the
text-justify
value of their nearest common ancestor.
Space distributed by justification is
in addition to
the spacing defined by the
letter-spacing
or
word-spacing
properties.
When such additional space is distributed to a
word separator
justification opportunity
it is applied under the same rules as for
word-spacing
Similarly, when space is distributed to an
justification opportunity
between
two
typographic character units
should be applied under the same rules as for
letter-spacing
A justification algorithm may divide
justification opportunities
into different priority levels.
All
justification opportunities
within a given level
are expanded or compressed at the same priority,
regardless of which
typographic character units
created that opportunity.
For example, if
justification opportunities
between two Han characters
and between two Latin letters are defined to be at the same level
(as they are in the
inter-character
justification style),
they are not treated differently because they originate from different
typographic character units
It is not defined in this level
whether or how other factors
(such as font size, letter-spacing, glyph shape, position within the line, etc.)
may influence the distribution of space to
justification opportunities
within the line.
The UA may enable or break optional ligatures or use other font features
such as alternate glyphs or glyph compression
to help justify the text under any method.
This behavior is not controlled by this level of CSS.
However, UAs
must not
break required ligatures
or otherwise disable features required to correctly shape complex scripts.
If a
justification opportunity
exists within a line,
and
text alignment
specifies
full justification (
justify
) for that line,
it must be justified.
6.4.2.
Handling Symbols and Punctuation
When determining
justification opportunities
typographic character unit
from the Unicode Symbols (S*) and Punctuation (P*) classes
is generally treated the same as a
typographic letter unit
of the same script
(or, if the character’s script property is Common,
then as a
typographic letter unit
of the dominant script).
However, by typographic tradition there may be additional rules
controlling the justification of symbols and punctuation.
Therefore, the UA may reassign specific characters
or introduce additional levels of prioritization
to handle
justification opportunities
involving symbols and punctuation.
For example, there are traditionally no
justification opportunities
between consecutive
U+2014 Em Dash ‘—’,
U+2015 Horizontal Bar ‘―’,
U+2026 Horizontal Ellipsis ‘…’,
or U+2025 Two Dot Leader ‘‥’
characters
[JLREQ]
thus a UA might assign these characters to a “never” prioritization level.
As another example, certain fullwidth punctuation characters
(such as U+301A Left White Square Bracket ‘〚’)
are considered to contain a
justification opportunity
in Japanese.
The UA might therefore assign these characters to a higher prioritization
level than the opportunities between ideographic characters.
6.4.3.
Unexpandable Text
If the inline contents of a line cannot be stretched to the full width of the line box,
then they must be aligned as specified by the
text-align-last
property.
(If
text-align-last
is
justify
, then
they must be aligned as for
center
.)
6.4.4.
Cursive Scripts
Justification
must not
introduce gaps between the joined
typographic letter units
of
cursive scripts
such as Arabic.
If it is able, the UA
may
translate space distributed to
justification opportunities
within a run of such
typographic letter units
into some form of cursive elongation for that run.
It otherwise
must
assume that no
justification opportunity
exists
between any pair of
typographic letter units
in
cursive script
(regardless of whether they join).
The following are examples of unacceptable justification:
Adding gaps between every pair of Arabic letters
Adding gaps between every pair of unjoined Arabic letters
Some font designs allow for the use of the tatweel character for justification.
A UA that performs tatweel-based justification must properly handle the rules for its use.
Note that correct insertion of tatweel characters depends on context, including
the letter-combinations involved, location within the word, and location of the word within the line.
6.4.5.
Minimum Requirements for
auto
Justification
For
auto
justification, this specification does not define
what all of the
justification opportunities
are,
how they are prioritized, or
when and how multiple levels of
justification opportunities
interact.
However, it does require that
Unless contraindicated by the typographic traditions of the
content language
or adjacent symbols/punctuation,
each of the following provides a
justification opportunity
Word separators
The boundary between a
typographic character unit
of any
block scripts
and any other
typographic character unit
The boundary between a
typographic character unit
of any
clustered scripts
and any other
typographic character unit
All
letters
belonging to all
block scripts
are treated the same,
and all
letters
belonging to all
clustered scripts
are treated the same.
For example, no distiction is made between
the justification opportunity between a Han letter followed by another Han letter,
vs. the justification opportunity between a Han letter followed by a Hangul letter.
Further information on text justification can be found in (or submitted to)
“Approaches to Full Justification”
which indexes by writing system and language,
and is maintained by the
W3C Internationalization Working Group
[JUSTIFY]
7.
Spacing
CSS offers control over text spacing
via the
word-spacing
and
letter-spacing
properties, which specify additional space
around
word separators
or between
typographic character units
, respectively.
7.1.
Word Spacing: the
word-spacing
property
Name:
word-spacing
Value:
normal

Initial:
normal
Applies to:
text
Inherited:
yes
Percentages:
N/A
Computed value:
an absolute length
Canonical order:
n/a
Animation type:
by computed value type
This property specifies additional spacing
between “words”.
Missing values are assumed to be
word-spacing:normal
Values are interpreted as defined below:
normal
No additional spacing is applied.
Computes to zero.

Specifies extra spacing
in addition to
the intrinsic inter-word spacing defined by the font.
Additional spacing is applied to each
word separator
left in the text after the
white space processing rules
have been applied,
and should be applied half on each side of the character
unless otherwise dictated by typographic tradition.
Values may be negative, but there may be implementation-dependent limits.
Word-separator characters
are
typographic character units
whose primary purpose and general usage is to separate words.
In
[UNICODE]
this includes (but is not exhaustively defined as)
the space (U+0020), the no-break space (U+00A0), the Ethiopic word space (U+1361),
the Aegean word separators (U+10100,U+10101), the Ugaritic word divider (U+1039F),
and the Phoenician Word Separator (U+1091F).
Note:
Neither punctuation in general,
nor fixed-width spaces (such as U+3000 and U+2000 through U+200A),
are considered
word-separator characters
because even though they frequently happen to separate words,
their primary purpose is not to separate words.
If there are no
word-separator characters
or if a word-separating character has a zero advance width
(such as the zero width space U+200B)
then the user agent must not create an additional spacing between words.
7.2.
Tracking: the
letter-spacing
property
Name:
letter-spacing
Value:
normal

Initial:
normal
Applies to:
inline boxes
and text
Inherited:
yes
Percentages:
n/a
Computed value:
an absolute length
Canonical order:
n/a
Animation type:
by computed value type
This property specifies additional spacing (commonly called
tracking
between adjacent
typographic character units
Letter-spacing is applied after
bidi reordering
[CSS-WRITING-MODES-3]
and is in addition to
kerning
[CSS-FONTS-3]
and
word-spacing
Depending on the justification rules in effect,
user agents may further increase or decrease the space between
typographic character units
in order to
justify text
Values have the following meanings:
normal
No additional spacing is applied. Computes to zero.

Specifies
additional
spacing between
typographic character units
Values may be negative, but there may be implementation-dependent limits.
For
legacy reasons
a computed
letter-spacing
of zero
yields a
resolved value
getComputedStyle()
return value)
of
normal
For the purpose of
letter-spacing
, each consecutive run of atomic
inlines (such as images and inline blocks) is treated as a single
typographic character unit
Letter-spacing must not be applied at the beginning of a line.
Whether letter-spacing is applied at the end of a line is undefined in this level.
When letter-spacing is not applied at the beginning or end of a line,
text always fits flush with the edge of the block.
p { letter-spacing: 1em; }

abc

a　b　c
a　b　c
UAs therefore
really should not
[RFC6919]
append letter spacing to the right or trailing edge of a line:
a　b　c
Letter spacing between two
typographic character units
effectively “belongs”
to the innermost element that contains the two
typographic character units
the total letter spacing between two adjacent
typographic character units
(after bidi reordering)
is specified by and rendered within
the innermost element that
contains
the boundary between the two
typographic character units
However, the UA may instead attach letter-spacing at element boundaries
to one or the other
typographic character unit
using the letter-spacing value pertaining to its containing element.
Note:
This secondary behavior is permitted in this level
due to Web-compat concerns.
An inline box is expected to only include
letter spacing between characters completely contained within that element,
thus excluding letter spacing on the right or trailing edge of the element:
p { letter-spacing: 1em; }

abbc

b　b
b　b
Consequently a given value of
letter-spacing
is expected
to only affect the spacing between characters
completely contained within the element for which it is specified:
p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abbc

b　　b
This further implies that applying
letter-spacing
to
an element containing only a single character
has no effect on the rendered result:
p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abc

Since letter spacing is inserted
after
RTL reordering,
the letter spacing applied to the inner span below likewise has no effect,
since after reordering the "c" doesn’t end up next to "א":
p { letter-spacing: 1em; }
span { letter-spacing: 2em; }

abcאבג

a　b
ב　ג
Letter spacing ignores invisible zero-width formatting characters
(such as those from the Unicode Cf category).
Spacing must be added as if those characters did not exist in the document.
For example,
letter-spacing
applied to
A​B
is identical to
AB
regardless of where any element boundaries might fall.
When the effective spacing between two characters is not zero
(due to either
justification
or a non-zero value of
letter-spacing
),
user agents should not apply optional ligatures,
i.e. those that are not defined as required
for fundamentally correct glyph shaping.
However, ligatures and other font features
specified via the low-level
font-feature-settings
property
take precedence over this rule.
See
CSS Fonts 3 §7.2 Feature precedence
For example, if the word “filial” is letter-spaced,
an “fi” ligature should not be used
as it will prevent even spacing of the text.
filial
vs
filial
Note:
In OpenType, required ligatures are expected
to be associated to the
rlig
feature.
All other ligatures are therefore considered optional.
In some cases, however, UA or platform heuristics
apply additional ligatures in order to handle broken fonts;
this specification does not define or override such exceptional handling.
7.2.1.
Cursive Scripts
If it is able, the UA
may
apply letter spacing to
cursive scripts
by translating the total extra space to be distributed to a run of such letters
into some form of cursive elongation (or compression, for negative tracking values) for that run
that results in an equivalent total expansion (or compression) of the run.
Otherwise, if the UA cannot expand text from a
cursive script
without breaking its cursive connections,
it
must not
apply spacing
between any pair of that script’s
typographic letter units
at all
(effectively treating each word as a single
typographic letter unit
for the purpose of letter-spacing).
Both cases will result in an effective spacing of zero between such letters;
however the former will preserve the sense of stretching out the text.
Below are some appropriate and inappropriate examples of spacing out Arabic text.
Original text
BAD
Even distribution of space between each letter.
Notice this breaks cursive joins!
OK
Distributing ∑
letter-spacing
by typographically-appropriate cursive elongation.
The resulting text is as long as the previous evenly-spaced example.
OK
Suppressing
letter-spacing
between Arabic letters.
Notice
letter-spacing
is nonetheless applied to non-Arabic characters (like
spaces
).
BAD
Applying
letter-spacing
only between non-joined letters.
This distorts typographic color and obfuscates word boundaries.
Note: Proper cursive elongation or compression of a text
can vary depending on the
script, typeface, language,
location within a word, location within a line,
implementation complexity, font capabilities,
and calligraphic preferences,
and may not be possible in certain cases at all.
It may involve the use of shortening ligatures,
swash variants, contextual forms,
elongation glyphs such as U+0640 ARABIC TATWEEL,
or other microtypography.
It is outside the scope of CSS to define rules for these effects.
Authors should avoid applying
letter-spacing
to cursive scripts
unless they are prepared to accept non-interoperable results.
7.3.
Shaping Across Element Boundaries
Text shaping
must
be broken at inline box boundaries
when any of the following are true
for any box whose boundary separates the two
typographic character units
Any of
margin
border
padding
separating the two
typographic character units
in the inline axis
is non-zero.
vertical-align
is not
baseline
The boundary is a
bidi isolation boundary
Text shaping
must not
be broken across inline box boundaries
when there is no effective change in formatting,
or if the only formatting changes do not affect the glyphs
(as in applying
text decoration
).
Text shaping
should not
be broken across inline box boundaries otherwise,
if it is reasonable and possible for that case given the limitations of the font technology.
An example of reasonable and possible shaping across boundaries
is Arabic shaping:
in many systems this is performed by the font engine,
allowing the font to provide variant glyphs
with potentially very sophisticated contextual shaping.
It’s not generally possible to rely on this system across a font change
unless the font engine has an API to provide context,
but it is straightforward and therefore quite reasonable
for an engine to work around this limitation by, for example,
using the zero-width-joiner (U+200D) or zero-width-non-joiner (U+200C)
as appropriate to solicit the correct choice of
initial/medial/final/isolated glyph.
An example of possible but not reasonable shaping across boundaries
is handling a font that is sensitive to 20 characters of context
on either side to choose its glyphs:
passing all the text before
and after
the string in question,
even through multiple inline boundaries with formatting changes,
is complicated.
The UA
could
handle such cases,
but is not required to,
as they are not typical or fundamentally required
by any modern writing system.
An example of impossible shaping accross boundaries
is a change in font weight partway through the word “and”
in a font where a ligature would replace
all three letters of the word “and”
with an ampersand glyph (“&”).
8.
Edge Effects
Edge effects control
the indentation of lines with respect to other lines in the block (
text-indent
and how content is measured at the start and end edges of a line (
hanging-punctuation
).
8.1.
First Line Indentation: the
text-indent
property
Name:
text-indent
Value:

&&
hanging
&&
each-line
Initial:
Applies to:
block containers
Inherited:
yes
Percentages:
refers to block container’s own
inline-axis
inner size
Computed value:
computed

value, plus any specified keywords
Canonical order:
per grammar
Animation type:
by computed value type
This property specifies the indentation applied to lines of inline
content in a block. The indent is treated as a margin applied to
the start edge of the line box.
Unless otherwise specified by the
each-line
and/or
hanging
keywords,
only lines that are the
first formatted line
[CSS2]
of an element are affected.
For example, the first line of an anonymous block box is only affected
if it is the first child of its parent element.
Values have the following meanings:

Gives the amount of the indent as an absolute length.

Gives the amount of the indent as a percentage of
the block container’s own
logical width
Percentages must be treated as
for the purpose of calculating
intrinsic size contributions
but are always resolved normally when performing layout.
Note:
This can lead to the element overflowing.
It is not recommended to use percentage indents and intrinsic sizing toghether.
each-line
Indentation affects the first line of each block container
and each line after a
forced line break
(but not lines after a
soft wrap break
).
hanging
Inverts which lines are affected.
If
text-align
is
start
and
text-indent
is
5em
in
left-to-right text with no floats present, then first line of text
will start 5em into the block:
Since CSS1 it has been possible to
indent the first line of a block element
5em by setting the 'text-indent' property
to '5em'.
If we add the
hanging
keyword,
then the first line will start flush,
but other lines will be indented 5em:
In CSS3 we can instead indent all other
lines of the block element by 5em
by setting the 'text-indent' property
to 'hanging 5em'.
Since the
text-indent
property only affects the “first formatted line”,
a line after a forced break will not be indented.
For example, in the middle of
this paragraph is an equation,
which is centered:
x + y = z
The first line after the equation
is flush (else it would look like
we started a new paragraph).
However, sometimes (as in poetry or code),
it is appropriate to indent each line
that happens to be long enough to wrap.
In the following example,
text-indent
is given a value of
3em hanging each-line
giving the third line of the poem a hanging indent
where it soft-wraps at the block’s right boundary:
In a short line of text
There need be no wrapping,
But when we go on and on and on
and on,
Sometimes a soft break
Can help us stay on the page.
Note: Since the
text-indent
property inherits,
when specified on a block element, it will affect descendant
inline-block elements.
For this reason, it is often wise to specify 'text-indent: 0' on
elements that are specified 'display: inline-block'.
8.2.
Hanging Glyphs
When a glyph at the start or end edge of a line
hangs
it is not considered
when measuring the line’s contents for fit, alignment, or justification.
Depending on the line’s alignment/justification, this can
result in the mark being placed outside the line box.
The
hanging
glyph is also not taken into account
when computing intrinsic sizes (min-content size and max-content size),
and any sizes derived thereof.
(The interaction of this measurement and kerning is currently UA-defined;
the CSSWG
welcomes advice
on this point.)
hanging
glyph
is still enclosed inside its parent inline box
and still participates in text justification:
its character advance is just not measured when determining
how much content fits on the line,
how much the line’s contents need to be expanded or compressed for justification,
or how to position the content within the line box for text alignment.
Effectively, the
hanging
glyph character advance
is re-interpreted as an additional negative margin
on the affected edge of its parent
inline box
the line is otherwise laid out as usual.
An overflowing
hanging glyph
should typically be considered
ink overflow
[CSS-OVERFLOW-3]
so as to avoid creating unnecessary scrollbars,
but the UA may treat it as
scrollable overflow
when the content is editable
or in other circumstances where treating it as
scrollable overflow
would be useful to the user.
In some cases, a glyph at the end of a line
can
conditionally hang
it
hangs
only if it does not otherwise fit in the line prior to justification.
It is not considered when measuring the line’s contents for fit;
however, any part of it that does not fit
is considered to
hang
Glyphs that
conditionally hang
are not taken into account
when computing
min-content sizes
and any sizes derived thereof,
but they are taken into account for
max-content sizes
and any sizes derived thereof.
Non-zero inline-axis borders or padding between
hang
able glyph and the edge of the line prevent the glyph from hanging.
For example, a period at the end of an inline box with end padding
does not
hang
at the end edge of a line.
Multiple adjacent glyphs can hang together,
however there may be limits on how many are allowed to hang
(e.g. at most one punctuation character may
hang
at each edge of the line).
8.2.1.
Hanging Punctuation: the
hanging-punctuation
property
Name:
hanging-punctuation
Value:
none
[ first
||
[ force-end
allow-end ]
||
last ]
Initial:
none
Applies to:
text
Inherited:
yes
Percentages:
n/a
Computed value:
specified keyword(s)
Canonical order:
per grammar
Animation type:
discrete
This property determines whether a punctuation mark, if one is present,
hangs
and may be placed outside the line box (or in the indent)
at the start or at the end of a line of text.
Note: If there is not sufficient padding on the
block container,
hanging-punctuation
can trigger overflow.
Values have the following meanings:
none
No punctuation character is made to
hang
first
An opening bracket or quote at the start of the
first
formatted line
of an element
hangs
This applies to all characters in the Unicode categories Ps, Pf, Pi
plus the ASCII quote marks “'” U+0027 and “"” U+0022.
last
A closing bracket or quote at the end of the
last formatted line of an element
hangs
This applies to all characters in the Unicode categories Pe, Pf, Pi
plus the ASCII quote marks “'” U+0027 and “"” U+0022.
force-end
stop or comma
at the end of a line
hangs
allow-end
stop or comma
at the end of a line
conditionally hangs
At most one punctuation character may
hang
at each edge of the line.
Stops and commas
allowed to
hang
include:
U+002C
COMMA
U+002E
FULL STOP
U+060C
ARABIC COMMA
U+06D4
ARABIC FULL STOP
U+3001
IDEOGRAPHIC COMMA
U+3002
IDEOGRAPHIC FULL STOP
U+FF0C
FULLWIDTH COMMA
U+FF0E
FULLWIDTH FULL STOP
U+FE50
SMALL COMMA
U+FE51
SMALL IDEOGRAPHIC COMMA
U+FE52
SMALL FULL STOP
U+FF61
HALFWIDTH IDEOGRAPHIC FULL STOP
U+FF64
HALFWIDTH IDEOGRAPHIC COMMA
The UA may include other characters as appropriate.
Note: The CSS Working Group would appreciate if UAs including
other characters would
inform the working group
of such additions.
The
allow-end
and
force-end
are two variations of
hanging punctuation used in East Asia.
p {
text-align: justify;
hanging-punctuation: allow-end;
p {
text-align: justify;
hanging-punctuation: force-end;
The punctuation at the end of the first line for
allow-end
does not hang, because it fits without hanging.
However, if
force-end
is used, it is forced to hang.
The justification measures the line without the hanging punctuation.
Therefore when the line is expanded, the punctuation is pushed outside the line.
8.3.
Bidirectionality and Line Boxes
The
start
and
end
sides of a line box
are determined by the
inline base direction
of the line box.
Although they usually match,
the
inline base direction
of a
line box
is distinct from the
inline base direction
of the
containing block
or the
bidi paragraph
The
line box
’s
inline base direction
affects
text-align-all
text-align-last
text-indent
, and
hanging-punctuation
i.e. the position and alignment of its contents with respect to its edges.
It does not affect the formatting or ordering of inline content
(which is controlled by the Unicode bidirectional algorithm
as applied by
[CSS-WRITING-MODES-3]
).
In most cases, a
line box
’s
inline base direction
is given by its
containing block
's computed
direction
However if its
containing block
has
unicode-bidi: plaintext
[CSS-WRITING-MODES-3]
If the
bidi paragraph
to which the
line box
belongs
(that is, the
bidi paragraph
for which the line box holds content)
has strong directionality,
the line box’s
inline base direction
is that direction.
If the
line box
is empty
(i.e. contains no
atomic inlines
or
characters other than the newline character, if any)
or otherwise has no strong directionality
(contains only weak or neutral characters),
its
inline base direction
is taken
from the preceding line box (if any),
or, if this is the first line box in the containing block,
from the
direction
property of the containing block.
(This can result in an RTL line box whose contents have an LTR base direction.)
In the following example,
assuming the

is a start-aligned preformatted block
display: block; white-space: pre; text-align: start
),
every other line is right-aligned:

فارسی
فارسی
فارسی

Because neutral characters (such as punctuation)
and isolated runs are skipped
when
finding the inline base direction of a plaintext bidi paragraph
the line box in the following example will be left-to-right
(and thus left-aligned given
text-align: start
),
as dictated by the first strong character, ‘h’:

“שלום!”, he said.

</p> <p>Hello!</p> <p>
Because of
unicode-bidi: plaintext
the “Hello!” is typeset LTR
(i.e. with the exclamation mark on the right side)
and left-aligned,
ignoring the containing block’s RTL
direction
This makes the empty line following it LTR as well,
which means that a caret on that line should appear at its left edge.
The empty first line, however, is right-aligned:
having no preceding line,
it assumes the RTL direction of its containing block.
Appendix A:
Text Processing Order of Operations
The following list defines the order of text operations.
(Implementations are not bound to this order as long as the resulting layout is the same.)
white space processing
part I (pre-wrapping)
text transformation
text combination
text orientation
[CSS-WRITING-MODES-3]
text wrapping
while applying per line:
indentation
bidirectional reordering
[CSS2]
[CSS-WRITING-MODES-3]
white space processing
part II
font/glyph selection and positioning
[CSS2]
[CSS-FONTS-3]
letter-spacing
and
word-spacing
hanging punctuation
justification
(which may affect glyph selection and/or text wrapping, looping back into that step)
text alignment
Appendix B: Conversion to Plaintext
This appendix is normative for the purpose of plaintext copy-paste operations.
When a CSS-rendered document is converted to a plaintext format,
it is expected that:
The
text-transform
property has no effect.
§ 4.1.1 Phase I: Collapsing and Transformation
is applied and any sequence of
collapsible
white space
at the beginning of a
block
or immediately following a
forced line break
is removed.
Appendix C: Default UA Stylesheet
This appendix is informative,
and is to help UA developers to implement a default stylesheet for HTML,
but UA developers are free to ignore or modify as appropriate.
/* make option elements align together */
option { text-align: match-parent; }
Appendix D: Scripts and Spacing
This appendix is normative.
Typographic behavior varies somewhat by language, but varies drastically by writing system.
This appendix categorizes some common
scripts
in Unicode 6.0
according to their justification and spacing behavior.
Category descriptions are descriptive, not prescriptive;
the determining factor is the prioritization of
justification opportunities
block scripts
CJK and by extension all Wide characters (see
[UAX11]
.)
The following
Unicode scripts
are included:
Bopomofo, Han, Hangul, Hiragana, Katakana, and Yi.
Characters of the
East Asian Width property
Wide
and
Fullwidth
are also included,
but
Ambiguous
characters are included only if
the
writing system
is
Chinese
Korean
, or
Japanese
clustered scripts
Clustered scripts have discrete units
and break only at word boundaries,
but do not use visible word separators.
They prioritize stretching spaces,
but comfortably admit inter-character spacing for justification.
The clustered scripts include, but are not limited to, the following
Unicode scripts
Khmer,
Lao,
Myanmar,
New Tai Lue,
Tai Le,
Tai Tham,
Tai Viet,
Thai
cursive scripts
Cursive scripts do not admit gaps between their letters for either justification or
letter-spacing
The following
Unicode scripts
are included:
Arabic,
Mandaic,
Mongolian,
N’Ko,
Phags Pa,
Syriac
Note:
Indic scripts with baseline connectors
(such as Devanagari and Gujarati)
are not
considered
cursive scripts
and
do
admit such gaps
between
typographic character units
See
[ILREQ]
User agents should update this list as they update their Unicode support
to handle as-yet-unencoded cursive scripts in future versions of Unicode,
and are encouraged to ask the CSSWG to update this spec accordingly.
Appendix E.
Characters and Properties
Unicode defines four code point-level properties that are referenced
in CSS typesetting:
East Asian width property
Defined in
[UAX11]
and given as the
East_Asian_Width
property
in the Unicode Character Database
[UAX44]
general category
Defined in
[UAX44]
and given as the
General_Category
property
in the Unicode Character Database
[UAX44]
script property
Defined in
[UAX24]
and given as the
Script
property
in the Unicode Character Database
[UAX44]
(UAs must include any ScriptExtensions.txt assignments in this mapping.)
Vertical Orientation
Defined in
[UTR50]
as the Vertical_Orientation property
and given in the UTR50 data file.
Unicode defines properties for individual code points, but sometimes
it is necessary to determine the properties of a
typographic character unit
For the purposes of CSS Text,
the properties of a
typographic character unit
are given by
the base character of its first
grapheme cluster
—except in two cases:
Grapheme clusters
formed with an Enclosing Mark (
Me
) of the Common script
are considered to be Other Symbols (
So
) in the Common script.
They are assumed to have the same Unicode properties as the Replacement Character U+FFFD.
Grapheme clusters formed with a Space Separator (
Zs
) as the base
are considered to be Modifier Symbols (
Sk
).
They are assumed to have the same East Asian Width property as the base,
but take their other properties from the first combining character in the sequence.
Appendix F.
Identifying the Content Writing System
This appendix is normative.
While most languages have a preferred writing system,
some have multiple, and
most can also be transcribed into one or more foreign writing systems.
As a common example, most languages have at least one Latin transcription,
and can thus be written in the Latin writing system.
Transcribed texts typically adopt the typographic conventions of the writing system:
for example Japanese “romaji” and Chinese Pinyin use Latin letters and word spaces,
and follow Latin line-breaking and justification practices accordingly.
As another example, historical ideographic Korean
ko-Hani
does not use word spaces,
and should therefore be typeset similar to Chinese
rather than modern Korean.
In
[HTML]
or any other
document language
using
[BCP47]
to declare the
content language
authors can disambiguate or indicate the use of an atypical writing system
with script subtags.
For example, to indicate use of the Latin writing system
for languages which don’t natively use it,
the
-Latn
script subtag can be added,
e.g.
ja-Latn
for Japanese romaji.
Other subtags exist for other writing systems,
see
[ISO15924]
and the
ISO15924 script tag registry
Some common/historical examples of using
[BCP47]
tags with script subtags:
zh-Latn
Chinese, written in Latin transcription.
ko-Hani
Korean, written in Hanja (Chinese ideographic characters).
tr-Arab
Turkish, written in Arabic script.
mn-Cyrl
Mongolian, written in Cyrillic.
mn-Mong
Mongolian, written in traditional Mongolian script.
However,
[BCP47]
script subtags are not typically used
(and are in fact discouraged)
for languages strongly associated with a single writing system:
instead that writing system is expected to be implied
when no other is specified.
IANA maintains a database of various languages’ most common writing system
via the
Suppress-Script
field in its
language subtag registry
for this purpose.
Note:
More advice on language tagging can be found in
the
Internationalization Working Group
’s
“Language tags in HTML and XML”
and
“Choosing a Language Tag”
When no writing system is explicitly indicated,
UAs should assume the most common writing system
of the declared
content language
for language-sensitive typographic behaviors
such as line-breaking or justification.
However, UAs must not assume that writing system
if the author has explicitly declared a different one.
If the UA has no language-specific knowledge
of a particular language and writing system combination,
it must use the typographic conventions of the declared writing system
(assuming the conventions of a different language if necessary),
not the conventions of the declared language in an assumed writing system,
which would be inappropriate to the declared writing system.
The full correspondence between languages and their most common writing systems
is out of scope for this document.
However, User Agents must assume at least the following:
If the
content language
is Chinese and the
writing system
is unspecified,
or for any
content language
if the
writing system
to specified to be one of the
Hant
Hans
Hani
Hanb
, or
Bopo
[ISO15924]
codes,
then the
writing system
is
Chinese
If the
content language
is Japanese and the
writing system
is unspecified,
or for any
content language
if the
writing system
to specified to be one of the
Jpan
Hrkt
Hira
or
Kana
[ISO15924]
codes,
then the
writing system
is
Japanese
If the
content language
is Korean and the
writing system
is unspecified,
or for any
content language
if the
writing system
to specified to be one of the
Kore
Hang
, or
Jamo
[ISO15924]
codes,
then the
writing system
is
Korean
The
writing system
is only considered to be
unknown
if the
content language
itself is unknown,
or if it explicitly indicates an unknown writing system.
Note:
Mere omission of the
writing system
information when the
content language
is declared
means the that the
writing system
is implied, not unknown.
Appendix G.
Small Kana Mappings
Small Kana Map to Full-size Kana
Small
Full-size
ぁ U+3041
あ U+3042
ぃ U+3043
い U+3044
ぅ U+3045
う U+3046
ぇ U+3047
え U+3048
ぉ U+3049
お U+304A
ゕ U+3095
か U+304B
ゖ U+3096
け U+3051
っ U+3063
つ U+3064
ゃ U+3083
や U+3084
ゅ U+3085
ゆ U+3086
ょ U+3087
よ U+3088
ゎ U+308E
わ U+308F
ァ U+30A1
ア U+30A2
ィ U+30A3
イ U+30A4
ゥ U+30A5
ウ U+30A6
ェ U+30A7
エ U+30A8
ォ U+30A9
オ U+30AA
ヵ U+30F5
カ U+30AB
ㇰ U+31F0
ク U+30AF
ヶ U+30F6
ケ U+30B1
ㇱ U+31F1
シ U+30B7
ㇲ U+31F2
ス U+30B9
ッ U+30C3
ツ U+30C4
ㇳ U+31F3
ト U+30C8
ㇴ U+31F4
ヌ U+30CC
ㇵ U+31F5
ハ U+30CF
ㇶ U+31F6
ヒ U+30D2
ㇷ U+31F7
フ U+30D5
ㇸ U+31F8
ヘ U+30D8
ㇹ U+31F9
ホ U+30DB
ㇺ U+31FA
ム U+30E0
ャ U+30E3
ヤ U+30E4
ュ U+30E5
ユ U+30E6
ョ U+30E7
ヨ U+30E8
ㇻ U+31FB
ラ U+30E9
ㇼ U+31FC
リ U+30EA
ㇽ U+31FD
ル U+30EB
ㇾ U+31FE
レ U+30EC
ㇿ U+31FF
ロ U+30ED
ヮ U+30EE
ワ U+30EF
ｧ U+FF67
ｱ U+FF71
ｨ U+FF68
ｲ U+FF72
ｩ U+FF69
ｳ U+FF73
ｪ U+FF6A
ｴ U+FF74
ｫ U+FF6B
ｵ U+FF75
ｯ U+FF6F
ﾂ U+FF82
ｬ U+FF6C
ﾔ U+FF94
ｭ U+FF6D
ﾕ U+FF95
ｮ U+FF6E
ﾖ U+FF96
Privacy and Security Considerations
This specification introduces no new security considerations.
This specification leaks the user’s installed hyphenation and line-breaking dictionaries.
Acknowledgements
This specification would not have been possible without the help from:
Ayman Aldahleh, David Baron, Bert Bos, Mike Bemford,
Tantek Çelik, James Clark, Emilio Cobos Álvarez,
Stephen Deach, John Daggett, Martin Dürst,
Laurie Anna Edlund, Ben Errez, Javier Fernandez, Yaniv Feinberg, Arye Gittelman,
Ian Hickson, Martin Heijdra, Dave Hyatt, Richard Ishida, Masayasu Ishikawa,
Michael Jochimsen, Jonathan Kew,
Aharon Lanin, Eric LeVine, Ambrose Li, Håkon Wium Lie, Chris Lilley,
Ken Lunde, Myles Maxfield, Nat McCully, IM Mincheol, Shinyu Murakami, Paul Nelson,
Addison Phillips, Chris Pratley, Xidorn Quan, Marcin Sawicki,
Arnold Schrijver, Rahul Sonnad, Alan Stearns, Michel Suignard, Takao Suzuki,
Frank Tang, Chris Thrasher, Etan Wexler, Chris Wilson, Masafumi Yabe
and Steve Zilles.
Changes
See
Disposition of Comments
covering all comments since 2013.
Changes from the
19 November 2020 Working Draft
Defined
word separator
a bit more precisely.
Issue 3878
Clarified that Indic scripts are not
cursive scripts
Issue 3566
Distinguished between properties that apply to
inline boxes
and those that apply to text directly
(which can be passed through when applied to an element with
display: contents
).
Issue 5303
Clarified
segment break
interaction with DOM/HTML.
Issue 5147
Miscellaneous other editorial improvements.
Changes from the
29 April 2020 Working Draft
Made
segment break transformation rules
UA-defined in this level.
5086
Allow
tab-size
to apply to inline boxes.
Issue 5489
Allow UAs to apply letter-spacing to one side of each character instead of between characters.
Issue 1518
Make plaintext line boxes belonging to bidi-neutral paragraphs
take their directionality from the previous line box rather than defaulting to LTR.
Issue 4405
Treat Carriage Returns (U+000D) as spaces for rendering.
Issue 5410
Editorial revisement of
§ 1.3 Languages and Typesetting
and
Appendix F.
Identifying the Content Writing System
Miscellaneous other editorial fixes and minor clarifications.
Changes from the
13 November 2019 Working Draft
Allow trailing OGHAM SPACE MARK to be trimmed.
Issue 4893
Revert wrapping behavior of
atomic inlines
due to Web-compat.
Issue 4575
Adjust
line-break
rules affecting certain hyphens and hyphen-like characters.
Issue 4419
Redefine hanging glyphs as
ink overflow
in most cases.
Issue 4297
Redefine line break transformation rules to evaluate context by Unicode code block.
Discussion
Miscellaneous editorial improvements.
Changes from the
12 December 2018 Working Draft
Normatively reference Unicode text processing.
Issue 3474
Clarify how out-of-flow elements and inline element boundaries do not affect text processing.
Remove control code exception for FORM FEED U+000C.
Issue 855
Use
allow-end
hanging rules rather than
force-end
rules for trailing white space;
define how it impacts intrinsic size contributions of text.
Issue 3440
Define interaction of bidi reordering and trailing space trimming.
Issue 4308
Generalize the logic that handles spaces at the end of lines
to apply to additional space separators.
Issue 3879
Tighten up definition of
break-spaces
value.
Fix up references to UAX14 line breaking classes.
(Issue
3516
and
3517
Clarify that word separators are not prioritized for breaking under
word-break: break-all
or
line-break: anywhere
Mark the behavior of
line-break
word-break
, and
overflow-wrap
at element boundaries undefined.
Issue 3897
Require breaking wrappable text even when dictionary resources are unavailable.
Issue 4284
Define proprietary
word-break: break-word
as a deprecated syntax for
overflow-wrap: anywhere
since it is required by Web-compat.
Remove stray reference to percentage
word-spacing
values.
Clarify that
hyphens: none
does not suppress wrapping opportunities after U+002D or U+2010.
Miscellaneous other minor clarifications and editorial improvements.
Changes from the
6 December 2018 Working Draft
Changes between 6 December 2018 and 12 December 2018 consist of
some minor cleanup in the line breaking section
and deferring

values of
word-spacing
to Level 4
with the expectation that they will be redefined
(see discussion in
issue 2165
).
Changes from the
October
2013 CSS3 Text
LCWD
Numerous significant changes were made
between the
10 October 2013 Last Call Working Draft
and the
6 December 2018 Working Draft
in response to
comments
oftentimes overwriting or reverting earlier changes.
While the general scope and approach of this specification is unchanged,
myriad details did change.
A handful of the more significant changes are highlighted below:
Switched
tab-size
to use

instead of

so that it is animatable,
and defined it to also account for
letter-spacing
and
word-spacing
Made
text-align
a shorthand of
text-align-last
and the new
text-align-all
property.
Removed dependence of
text-align-last
on
text-align: justify
since the problem it solves is now solved by the shorthanding relationship.
Qualified that only lowercase letters are titlecased for
text-transform: capitalize
; uppercase letters remain unaffected.
For
word-break: break-all
, included non-letters that are treated as letter-like in
[UAX14]
to handle symbols better.
Added
line-break: anywhere
and
overflow-wrap: anywhere
Tweaked handling of Ambiguous characters during
segment break transformation
Most of the changes since 2013 are details not tracked in this list.
If you have last reviewed this specification
before publication of the
6 December 2018 Working Draft
it’s probably advisable to simply read it from scratch.
For an exhaustive list of changes since 2013,
please see the
css-text-3
and
css3-text
commit logs
or the
diff between 2013 and 2018
For an exhaustive list of issues addressed,
see the
Disposition of Comments
Conformance
Document conventions
Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes.
[RFC2119]
Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with
class="example"
like this:
This is an example of an informative example.
Informative notes begin with the word “Note” and are set apart from the
normative text with
class="note"
, like this:
Note, this is an informative note.
Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with

, like
this:
UAs MUST provide an accessible alternative.
Conformance classes
Conformance to this specification
is defined for three conformance classes:
style sheet
CSS
style sheet
renderer
UA
that interprets the semantics of a style sheet and renders
documents that use them.
authoring tool
UA
that writes a style sheet.
A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
Partial implementations
So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers
must
treat as invalid (and
ignore
as appropriate
) any at-rules, properties, property values, keywords,
and other syntactic constructs for which they have no usable level of
support. In particular, user agents
must not
selectively
ignore unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid
(as unsupported values must be), CSS requires that the entire declaration
be ignored.
Implementations of Unstable and Proprietary Features
To avoid clashes with future stable CSS features,
the CSSWG recommends
following best practices
for the implementation of
unstable
features and
proprietary extensions
to CSS.
Non-experimental implementations
Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they
can demonstrate to be correctly implemented according to spec.
To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group.
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at
Questions should be directed to the
public-css-testsuite@w3.org
mailing list.
CR exit criteria
For this specification to be advanced to Proposed Recommendation,
there must be at least two independent, interoperable implementations
of each feature. Each feature may be implemented by a different set of
products, there is no requirement that all features be implemented by
a single product. For the purposes of this criterion, we define the
following terms:
independent
each implementation must be developed by a
different party and cannot share, reuse, or derive from code
used by another qualifying implementation. Sections of code that
have no bearing on the implementation of this specification are
exempt from this requirement.
interoperable
passing the respective test case(s) in the
official CSS test suite, or, if the implementation is not a Web
browser, an equivalent test. Every relevant test in the test
suite should have an equivalent test created if such a user
agent (UA) is to be used to claim interoperability. In addition
if such a UA is to be used to claim interoperability, then there
must one or more additional UAs which can also pass those
equivalent tests in the same way for the purpose of
interoperability. The equivalent tests must be made publicly
available for the purposes of peer review.
implementation
a user agent which:
implements the specification.
is available to the general public. The implementation may
be a shipping product or other publicly available version
(i.e., beta version, preview release, or "nightly build").
Non-shipping product releases must have implemented the
feature(s) for a period of at least one month in order to
demonstrate stability.
is not experimental (i.e., a version specifically designed
to pass the test suite and is not intended for normal usage
going forward).
The specification will remain Candidate Recommendation for at least
six months.
Index
Terms defined by this specification
allow-end
, in §8.2.1
anywhere
value for line-break
, in §5.3
value for overflow-wrap
, in §5.5
auto
value for hyphens
, in §5.4
value for line-break
, in §5.3
value for text-align-last
, in §6.3
value for text-justify
, in §6.4
bidi formatting characters
, in §4.1.1
block scripts
, in §Unnumbered section
break-all
, in §5.2
break-spaces
, in §3
break-word
value for overflow-wrap
, in §5.5
value for word-break
, in §5.2
capitalize
, in §2.1
center
, in §6.1
character
, in §1.4
Chinese
, in §Unnumbered section
clustered scripts
, in §Unnumbered section
collapsible
, in §4.1.1
collapsible white space
, in §4.1.1
conditionally hang
, in §8.2
content language
, in §1.3
content writing system
, in §1.3
cursive script
, in §Unnumbered section
distribute
, in §6.4
document white space
, in §4.1
document white space characters
, in §4.1
each-line
, in §8.1
East Asian Width property
, in §Unnumbered section
end
, in §6.1
first
, in §8.2.1
forced line break
, in §5
force-end
, in §8.2.1
full-size
, in §Unnumbered section
full-size kana
, in §Unnumbered section
full-size-kana
, in §2.1
full-width
, in §2.1
General Category
, in §Unnumbered section
grapheme cluster
, in §1.4
hang
, in §8.2
hanging
, in §8.1
hanging glyph
, in §8.2
hanging-punctuation
, in §8.2.1
hyphenate
, in §5.4
hyphenation
, in §5.4
hyphenation opportunity
, in §5.4
hyphens
, in §5.4
inter-character
, in §6.4
inter-word
, in §6.4
Japanese
, in §Unnumbered section
justification opportunity
, in §6.4.1
justify
, in §6.1
justify-all
, in §6.1
keep-all
, in §5.2
known
, in §Unnumbered section
Korean
, in §Unnumbered section
last
, in §8.2.1
left
, in §6.1

value for letter-spacing
, in §7.2
value for text-indent
, in §8.1
value for word-spacing
, in §7.1
letter
, in §1.4
letter-spacing
, in §7.2
line break
, in §5
line-break
, in §5.3
line breaking
, in §5
line breaking process
, in §5
loose
, in §5.3
lowercase
, in §2.1
manual
, in §5.4
match-parent
, in §6.1
none
value for hanging-punctuation
, in §8.2.1
value for hyphens
, in §5.4
value for text-justify
, in §6.4
value for text-transform
, in §2.1
normal
value for letter-spacing
, in §7.2
value for line-break
, in §5.3
value for overflow-wrap
, in §5.5
value for white-space
, in §3
value for word-break
, in §5.2
value for word-spacing
, in §7.1
nowrap
, in §3
other space separators
, in §4.1
overflow-wrap
, in §5.5

, in §8.1
pre
, in §3
pre-line
, in §3
preserved
, in §3
preserved white space
, in §3
pre-wrap
, in §3
right
, in §6.1
Script property
, in §Unnumbered section
segment break
, in §4
small
, in §Unnumbered section
small kana
, in §Unnumbered section
soft wrap break
, in §5
soft wrap opportunity
, in §5
spaces
, in §4.1
start
, in §6.1
stop or comma
, in §8.2.1
strict
, in §5.3
tabs
, in §4.1
tab size
, in §4.2
tab-size
, in §4.2
tab stop
, in §4.1.2
text-align
, in §6.1
text-align-all
, in §6.2
text-align-last
, in §6.3
text-indent
, in §8.1
text-justify
, in §6.4
text-transform
, in §2.1
tracking
, in §7.2
typographic character
, in §1.4
typographic character unit
, in §1.4
typographic letter unit
, in §1.4
Unicode category
, in §Unnumbered section
Unicode East Asian Width
, in §Unnumbered section
Unicode General Category
, in §Unnumbered section
Unicode Script
, in §Unnumbered section
unknown
, in §Unnumbered section
uppercase
, in §2.1
white space
, in §4.1
white-space
, in §3
white space characters
, in §4.1
word-break
, in §5.2
word separator
, in §7.1
word-separator character
, in §7.1
word-spacing
, in §7.1
word-wrap
, in §5.5
wrap
, in §5
wrapping
, in §5
writing system
, in §1.3
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
6.1.
Text Alignment: the text-align shorthand
Referenced in:
6.1.
Text Alignment: the text-align shorthand
Referenced in:
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
Referenced in:
6.1.
Text Alignment: the text-align shorthand
6.2.
Default Text Alignment: the text-align-all property
Referenced in:
5.1.
Line Breaking Details
8.3.
Bidirectionality and Line Boxes
Changes from the 13 November 2019 Working Draft
Referenced in:
Appendix B: Conversion to Plaintext
Referenced in:
4.1.2. Phase II: Trimming and Positioning
4.2.
Tab Character Size: the tab-size property
Referenced in:
8.3.
Bidirectionality and Line Boxes
(2)
(3)
Referenced in:
8.3.
Bidirectionality and Line Boxes
Changes from the 19 November 2020 Working Draft
Referenced in:
6.1.
Text Alignment: the text-align shorthand
Referenced in:
1.5.
Text Processing
7.2.
Tracking: the letter-spacing property
8.2.
Hanging Glyphs
Changes from the 19 November 2020 Working Draft
Referenced in:
4.1.1. Phase I: Collapsing and Transformation
Referenced in:
1.5.
Text Processing
Referenced in:
7.2.
Tracking: the letter-spacing property
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
8.3.
Bidirectionality and Line Boxes
(2)
(3)
(4)
(5)
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
8.2.
Hanging Glyphs
Changes from the 13 November 2019 Working Draft
Referenced in:
8.2.
Hanging Glyphs
(2)
Referenced in:
6.1.
Text Alignment: the text-align shorthand
Referenced in:
6.1.
Text Alignment: the text-align shorthand
Referenced in:
2.1.
Case Transforms: the text-transform property
Referenced in:
8.1.
First Line Indentation: the text-indent property
Referenced in:
8.1.
First Line Indentation: the text-indent property
Referenced in:
3.
White Space and Wrapping: the white-space property
Referenced in:
8.2.
Hanging Glyphs
Referenced in:
5.4.
Hyphenation: the hyphens property
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
8.2.
Hanging Glyphs
Referenced in:
Changes from the October
2013 CSS3 Text LCWD
Referenced in:
4.2.
Tab Character Size: the tab-size property
7.1.
Word Spacing: the word-spacing property
7.2.
Tracking: the letter-spacing property
Referenced in:
4.2.
Tab Character Size: the tab-size property
(2)
Changes from the October
2013 CSS3 Text LCWD
Referenced in:
Changes from the 6 December 2018 Working Draft
Referenced in:
8.1.
First Line Indentation: the text-indent property
(2)
Referenced in:
8.1.
First Line Indentation: the text-indent property
(2)
Referenced in:
8.1.
First Line Indentation: the text-indent property
(2)
Referenced in:
1.2.
Value Definitions
Referenced in:
2.1.
Case Transforms: the text-transform property
(2)
(3)
3.
White Space and Wrapping: the white-space property
(2)
(3)
(4)
(5)
4.2.
Tab Character Size: the tab-size property
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
(4)
5.4.
Hyphenation: the hyphens property
(2)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
6.1.
Text Alignment: the text-align shorthand
(2)
(3)
(4)
(5)
(6)
(7)
6.2.
Default Text Alignment: the text-align-all property
(2)
(3)
(4)
(5)
(6)
6.3.
Last Line Alignment: the text-align-last property
(2)
(3)
(4)
(5)
(6)
(7)
6.4.
Justification Method: the text-justify property
(2)
(3)
7.1.
Word Spacing: the word-spacing property
7.2.
Tracking: the letter-spacing property
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
Referenced in:
2.1.
Case Transforms: the text-transform property
(2)
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
Referenced in:
6.1.
Text Alignment: the text-align shorthand
8.3.
Bidirectionality and Line Boxes
(2)
(3)
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
(3)
8.3.
Bidirectionality and Line Boxes
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
(3)
8.3.
Bidirectionality and Line Boxes
Referenced in:
8.3.
Bidirectionality and Line Boxes
(2)
Referenced in:
8.3.
Bidirectionality and Line Boxes
(2)
(3)
Referenced in:
7.3.
Shaping Across Element Boundaries
Referenced in:
8.3.
Bidirectionality and Line Boxes
(2)
(3)
(4)
(5)
(6)
(7)
Referenced in:
8.1.
First Line Indentation: the text-indent property
Referenced in:
8.1.
First Line Indentation: the text-indent property
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
Referenced in:
1.4.
Characters and Letters
Referenced in:
7.2.
Tracking: the letter-spacing property
Referenced in:
5.2.
Breaking Rules for Letters: the word-break property
Referenced in:
4.
White Space Processing & Control Characters
Referenced in:
1.3.
Languages and Typesetting
(2)
Appendix F.
Identifying the Content Writing System
Terms defined by reference
[css-backgrounds-3]
defines the following terms:
border
[css-box-4]
defines the following terms:
margin
padding
[css-cascade-4]
defines the following terms:
inherit
inherited value
legacy name alias
shorthand property
[css-display-3]
defines the following terms:
atomic inline
block
block container
containing block
display
initial containing block
inline box
inline formatting context
out-of-flow
[css-fonts-4]
defines the following terms:
font-feature-settings
[css-inline-3]
defines the following terms:
baseline
line box
vertical-align
[CSS-OVERFLOW-3]
defines the following terms:
ink overflow
scrollable overflow
[css-position-3]
defines the following terms:
left
right
[CSS-RUBY-1]
defines the following terms:
ruby
[css-sizing-3]
defines the following terms:
inner size
intrinsic size contribution
intrinsic sizing
max-content size
min-content size
[CSS-VALUES-3]
defines the following terms:




[css-values-4]
defines the following terms:
&&

css-wide keywords
||
[CSS-WRITING-MODES-3]
defines the following terms:
direction
end
start
unicode-bidi
[css-writing-modes-4]
defines the following terms:
bidi paragraph
bidi-isolate
inline base direction
inline-axis
logical width
text-orientation
upright
[cssom-1]
defines the following terms:
resolved value
[HTML]
defines the following terms:
wbr
[INFRA]
defines the following terms:
normalize newlines
[selectors-4]
defines the following terms:
document language
References
Normative References
[CSS-BACKGROUNDS-3]
Bert Bos; Elika Etemad; Brad Kemper.
CSS Backgrounds and Borders Module Level 3
. 17 October 2017. CR. URL:
[CSS-BOX-4]
Elika Etemad.
CSS Box Model Module Level 4
. 21 April 2020. WD. URL:
[CSS-CASCADE-4]
Elika Etemad; Tab Atkins Jr..
CSS Cascading and Inheritance Level 4
. 18 August 2020. WD. URL:
[CSS-DISPLAY-3]
Tab Atkins Jr.; Elika Etemad.
CSS Display Module Level 3
. 18 December 2020. CR. URL:
[CSS-FONTS-3]
John Daggett; Myles Maxfield; Chris Lilley.
CSS Fonts Module Level 3
. 20 September 2018. REC. URL:
[CSS-FONTS-4]
John Daggett; Myles Maxfield; Chris Lilley.
CSS Fonts Module Level 4
. 17 November 2020. WD. URL:
[CSS-INLINE-3]
Dave Cramer; Elika Etemad; Steve Zilles.
CSS Inline Layout Module Level 3
. 27 August 2020. WD. URL:
[CSS-OVERFLOW-3]
David Baron; Elika Etemad; Florian Rivoal.
CSS Overflow Module Level 3
. 3 June 2020. WD. URL:
[CSS-POSITION-3]
Elika Etemad; et al.
CSS Positioned Layout Module Level 3
. 19 May 2020. WD. URL:
[CSS-RUBY-1]
Elika Etemad; et al.
CSS Ruby Layout Module Level 1
. 29 April 2020. WD. URL:
[CSS-SIZING-3]
Tab Atkins Jr.; Elika Etemad.
CSS Box Sizing Module Level 3
. 18 December 2020. WD. URL:
[CSS-VALUES-3]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 3
. 6 June 2019. CR. URL:
[CSS-VALUES-4]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 4
. 11 November 2020. WD. URL:
[CSS-WRITING-MODES-3]
Elika Etemad; Koji Ishii.
CSS Writing Modes Level 3
. 10 December 2019. REC. URL:
[CSS-WRITING-MODES-4]
Elika Etemad; Koji Ishii.
CSS Writing Modes Level 4
. 30 July 2019. CR. URL:
[CSS2]
Bert Bos; et al.
Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification
. 7 June 2011. REC. URL:
[CSSOM-1]
Simon Pieters; Glenn Adams.
CSS Object Model (CSSOM)
. 17 March 2016. WD. URL:
[RFC2119]
S. Bradner.
Key words for use in RFCs to Indicate Requirement Levels
. March 1997. Best Current Practice. URL:
[SELECTORS-4]
Elika Etemad; Tab Atkins Jr..
Selectors Level 4
. 21 November 2018. WD. URL:
[UAX11]
Ken Lunde 小林劍󠄁.
East Asian Width
. 18 January 2020. Unicode Standard Annex #11. URL:
[UAX14]
Christopher Chapman.
Unicode Line Breaking Algorithm
. 17 February 2020. Unicode Standard Annex #14. URL:
[UAX24]
Ken Whistler.
Unicode Script Property
. 17 February 2020. Unicode Standard Annex #24. URL:
[UAX29]
Mark Davis; Christopher Chapman.
Unicode Text Segmentation
. 19 February 2020. Unicode Standard Annex #29. URL:
[UAX44]
Ken Whistler; Laurențiu Iancu.
Unicode Character Database
. 4 March 2020. Unicode Standard Annex #44. URL:
[UAX9]
Mark Davis; Aharon Lanin; Andrew Glass.
Unicode Bidirectional Algorithm
. 12 February 2020. Unicode Standard Annex #9. URL:
[UNICODE]
The Unicode Standard
. URL:
[UTR50]
Ken Lunde 小林劍󠄁; Koji Ishii 石井宏治.
Unicode Vertical Text Layout
. 18 January 2020. Unicode Standard Annex #50. URL:
Informative References
[BCP47]
A. Phillips; M. Davis.
Tags for Identifying Languages
. September 2009. IETF Best Current Practice. URL:
[CLREQ]
Bobby Tung; et al.
Requirements for Chinese Text Layout中文排版需求
. 1 November 2020. WD. URL:
[CSS-TEXT-DECOR-3]
Elika Etemad; Koji Ishii.
CSS Text Decoration Module Level 3
. 13 August 2019. CR. URL:
[DOM]
Anne van Kesteren.
DOM Standard
. Living Standard. URL:
[HTML]
Anne van Kesteren; et al.
HTML Standard
. Living Standard. URL:
[ILREQ]
Swaran Lata.
Indic Layout Requirements
. 29 May 2020. WD. URL:
[INFRA]
Anne van Kesteren; Domenic Denicola.
Infra Standard
. Living Standard. URL:
[ISO15924]
Code for the representation of names of scripts.
International Organization for Standardization. 1998. ISO 15924:1998. Draft International Standard
[JIS4051]
Formatting rules for Japanese documents (『日本語文書の組版方法』).
Japanese Standards Association. 2004. JIS X 4051:2004. In Japanese
[JLREQ]
Hiroyuki Chiba; et al.
Requirements for Japanese Text Layout 日本語組版処理の要件(日本語版)
. 11 August 2020. NOTE. URL:
[JUSTIFY]
Elika Etemad; Richard Ishida.
Approches to Full Justification
. URL:
[RFC6919]
R. Barnes; S. Kent; E. Rescorla.
Further Key Words for Use in RFCs to Indicate Requirement Levels
. 1 April 2013. Experimental. URL:
[TYPOGRAPHY]
Richard Ishida.
Language enablement index
. 20 May 2020. WD. URL:
[XML10]
Tim Bray; et al.
Extensible Markup Language (XML) 1.0 (Fifth Edition)
. 26 November 2008. REC. URL:
[ZHMARK]
General Rules for Punctuation (《标点符号用法》).
2011. GB/T 15834―2011. In Chinese.
Property Index
Name
Value
Initial
Applies to
Inh.
%ages
Anim­ation type
Canonical order
Com­puted value
hanging-punctuation
none | [ first || [ force-end | allow-end ] || last ]
none
text
yes
n/a
discrete
per grammar
specified keyword(s)
hyphens
none | manual | auto
manual
text
yes
n/a
discrete
n/a
specified keyword
letter-spacing
normal |
normal
inline boxes and text
yes
n/a
by computed value type
n/a
an absolute length
line-break
auto | loose | normal | strict | anywhere
auto
text
yes
n/a
discrete
n/a
specified keyword
overflow-wrap
normal | break-word | anywhere
normal
text
yes
n/a
discrete
n/a
specified keyword
tab-size
|
text
yes
n/a
by computed value type
n/a
the specified number or absolute length
text-align
start | end | left | right | center | justify | match-parent | justify-all
start
block containers
yes
see individual properties
discrete
n/a
see individual properties
text-align-all
start | end | left | right | center | justify | match-parent
start
block containers
yes
n/a
discrete
n/a
keyword as specified, except for match-parent which computes as defined above
text-align-last
auto | start | end | left | right | center | justify | match-parent
auto
block containers
yes
n/a
discrete
n/a
specified keyword
text-indent
[ ] && hanging? && each-line?
block containers
yes
refers to block container’s own inline-axis inner size
by computed value type
per grammar
computed value, plus any specified keywords
text-justify
auto | none | inter-word | inter-character
auto
text
yes
n/a
discrete
n/a
specified keyword
text-transform
none | [capitalize | uppercase | lowercase ] || full-width || full-size-kana
none
text
yes
n/a
discrete
n/a
specified keyword
white-space
normal | pre | nowrap | pre-wrap | break-spaces | pre-line
normal
text
yes
n/a
discrete
n/a
specified keyword
word-break
normal | keep-all | break-all | break-word
normal
text
yes
n/a
discrete
n/a
specified keyword
word-spacing
normal |
normal
text
yes
N/A
by computed value type
n/a
an absolute length
word-wrap
normal | break-word | anywhere
normal
text
yes
n/a
discrete
n/a
specified keyword
#content-language
Referenced in:
1.3.
Languages and Typesetting
(2)
(3)
(4)
(5)
(6)
2.1.1.
Mapping Rules
(2)
5.1.
Line Breaking Details
5.4.
Hyphenation: the hyphens property
(2)
6.4.
Justification Method: the text-justify property
6.4.5.
Minimum Requirements for auto Justification
Appendix F.
Identifying the Content Writing System
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
#content-writing-system
Referenced in:
2.1.1.
Mapping Rules
5.3.
Line Breaking Strictness: the line-break property
(2)
Appendix D: Scripts and Spacing
Appendix F.
Identifying the Content Writing System
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
#character
Referenced in:
1.4.
Characters and Letters
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
#typographic-character-unit
Referenced in:
1.4.
Characters and Letters
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
2.1.
Case Transforms: the text-transform property
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
5.3.
Line Breaking Strictness: the line-break property
6.4.
Justification Method: the text-justify property
6.4.1.
Expanding and Compressing Text
(2)
(3)
(4)
(5)
(6)
(7)
6.4.2.
Handling Symbols and Punctuation
6.4.5.
Minimum Requirements for auto Justification
(2)
(3)
(4)
7.
Spacing
7.1.
Word Spacing: the word-spacing property
7.2.
Tracking: the letter-spacing property
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
7.3.
Shaping Across Element Boundaries
(2)
Appendix D: Scripts and Spacing
Appendix E.
Characters and Properties
(2)
#grapheme-cluster
Referenced in:
1.4.
Characters and Letters
(2)
(3)
(4)
Appendix E.
Characters and Properties
(2)
#typographic-letter-unit
Referenced in:
2.1.
Case Transforms: the text-transform property
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
(4)
6.4.
Justification Method: the text-justify property
(2)
6.4.2.
Handling Symbols and Punctuation
(2)
6.4.4.
Cursive Scripts
(2)
(3)
7.2.1.
Cursive Scripts
(2)
#letter
Referenced in:
2.1.
Case Transforms: the text-transform property
(2)
5.2.
Breaking Rules for Letters: the word-break property
6.4.5.
Minimum Requirements for auto Justification
(2)
#propdef-text-transform
Referenced in:
2.1.
Case Transforms: the text-transform property
(2)
(3)
(4)
2.1.1.
Mapping Rules
Appendix B: Conversion to Plaintext
Changes from the October
2013 CSS3 Text LCWD
#valdef-text-transform-capitalize
Referenced in:
2.1.1.
Mapping Rules
(2)
2.1.2.
Order of Operations
#valdef-text-transform-uppercase
Referenced in:
2.1.2.
Order of Operations
#valdef-text-transform-lowercase
Referenced in:
2.1.2.
Order of Operations
#valdef-text-transform-full-width
Referenced in:
2.1.2.
Order of Operations
(2)
#valdef-text-transform-full-size-kana
Referenced in:
2.1.2.
Order of Operations
#propdef-white-space
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.
White Space Processing & Control Characters
(2)
4.1.1. Phase I: Collapsing and Transformation
(2)
(3)
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
(5)
4.1.3.
Segment Break Transformation Rules
(2)
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
(2)
5.3.
Line Breaking Strictness: the line-break property
(2)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
#valdef-white-space-normal
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
(3)
(4)
(5)
4.1.1. Phase I: Collapsing and Transformation
(2)
4.1.2. Phase II: Trimming and Positioning
(2)
5.3.
Line Breaking Strictness: the line-break property
#valdef-white-space-pre
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
(3)
4.1.1. Phase I: Collapsing and Transformation
4.1.3.
Segment Break Transformation Rules
5.3.
Line Breaking Strictness: the line-break property
#valdef-white-space-nowrap
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.1.1. Phase I: Collapsing and Transformation
4.1.2. Phase II: Trimming and Positioning
(2)
5.3.
Line Breaking Strictness: the line-break property
#valdef-white-space-pre-wrap
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.1.1. Phase I: Collapsing and Transformation
(2)
4.1.2. Phase II: Trimming and Positioning
4.1.3.
Segment Break Transformation Rules
5.3.
Line Breaking Strictness: the line-break property
#valdef-white-space-break-spaces
Referenced in:
3.
White Space and Wrapping: the white-space property
4.1.1. Phase I: Collapsing and Transformation
(2)
4.1.2. Phase II: Trimming and Positioning
4.1.3.
Segment Break Transformation Rules
5.3.
Line Breaking Strictness: the line-break property
(2)
Changes from the 12 December 2018 Working Draft
#valdef-white-space-pre-line
Referenced in:
3.
White Space and Wrapping: the white-space property
4.1.1. Phase I: Collapsing and Transformation
4.1.2. Phase II: Trimming and Positioning
(2)
4.1.3.
Segment Break Transformation Rules
5.3.
Line Breaking Strictness: the line-break property
#preserved-white-space
Referenced in:
2.1.2.
Order of Operations
3.
White Space and Wrapping: the white-space property
(2)
(3)
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
4.2.
Tab Character Size: the tab-size property
(2)
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
(4)
(5)
#segment-break
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.
White Space Processing & Control Characters
(2)
(3)
(4)
4.1.1. Phase I: Collapsing and Transformation
(2)
4.1.3.
Segment Break Transformation Rules
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Changes from the 19 November 2020 Working Draft
#white-space
Referenced in:
1.
Introduction
(2)
2.1.2.
Order of Operations
3.
White Space and Wrapping: the white-space property
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
4.
White Space Processing & Control Characters
(2)
(3)
(4)
4.1.
The White Space Processing Rules
4.1.1. Phase I: Collapsing and Transformation
(2)
4.1.2. Phase II: Trimming and Positioning
4.1.3.
Segment Break Transformation Rules
5.2.
Breaking Rules for Letters: the word-break property
6.1.
Text Alignment: the text-align shorthand
Appendix B: Conversion to Plaintext
#spaces
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.
White Space Processing & Control Characters
4.1.1. Phase I: Collapsing and Transformation
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
4.1.3.
Segment Break Transformation Rules
(2)
(3)
5.
Line Breaking and Word Boundaries
5.2.
Breaking Rules for Letters: the word-break property
(2)
7.2.1.
Cursive Scripts
#tabs
Referenced in:
4.
White Space Processing & Control Characters
4.1.1. Phase I: Collapsing and Transformation
(2)
(3)
(4)
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
4.1.3.
Segment Break Transformation Rules
4.2.
Tab Character Size: the tab-size property
#other-space-separators
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
(3)
(4)
4.1.2. Phase II: Trimming and Positioning
(2)
5.2.
Breaking Rules for Letters: the word-break property
#collapsible-white-space
Referenced in:
4.
White Space Processing & Control Characters
4.1.1. Phase I: Collapsing and Transformation
(2)
(3)
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
4.1.3.
Segment Break Transformation Rules
(2)
Appendix B: Conversion to Plaintext
#tab-stop
Referenced in:
4.1.2. Phase II: Trimming and Positioning
(2)
6.1.
Text Alignment: the text-align shorthand
#propdef-tab-size
Referenced in:
4.1.2. Phase II: Trimming and Positioning
4.2.
Tab Character Size: the tab-size property
Changes from the 29 April 2020 Working Draft
Changes from the October
2013 CSS3 Text LCWD
#tab-size-dfn
Referenced in:
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
#line-break
Referenced in:
5.1.
Line Breaking Details
#forced-line-break
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
(3)
4.1.2. Phase II: Trimming and Positioning
5.1.
Line Breaking Details
(2)
6.3.
Last Line Alignment: the text-align-last property
8.1.
First Line Indentation: the text-indent property
Appendix B: Conversion to Plaintext
#wrapping
Referenced in:
3.
White Space and Wrapping: the white-space property
4.1.2. Phase II: Trimming and Positioning
5.3.
Line Breaking Strictness: the line-break property
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
5.6.
Shaping Across Intra-word Breaks
Appendix A:
Text Processing Order of Operations
#soft-wrap-break
Referenced in:
8.1.
First Line Indentation: the text-indent property
#line-breaking-process
Referenced in:
4.1.1. Phase I: Collapsing and Transformation
5.1.
Line Breaking Details
#soft-wrap-opportunity
Referenced in:
3.
White Space and Wrapping: the white-space property
(2)
4.1.1. Phase I: Collapsing and Transformation
(2)
(3)
5.
Line Breaking and Word Boundaries
(2)
(3)
(4)
(5)
(6)
5.1.
Line Breaking Details
(2)
(3)
(4)
(5)
(6)
(7)
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
(4)
(5)
(6)
5.3.
Line Breaking Strictness: the line-break property
5.4.
Hyphenation: the hyphens property
(2)
(3)
(4)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
5.6.
Shaping Across Intra-word Breaks
#propdef-word-break
Referenced in:
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
(2)
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
5.3.
Line Breaking Strictness: the line-break property
(2)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
5.6.
Shaping Across Intra-word Breaks
Changes from the 12 December 2018 Working Draft
(2)
(3)
Changes from the October
2013 CSS3 Text LCWD
#valdef-word-break-normal
Referenced in:
5.2.
Breaking Rules for Letters: the word-break property
(2)
#valdef-word-break-break-all
Referenced in:
5.2.
Breaking Rules for Letters: the word-break property
#propdef-line-break
Referenced in:
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
(2)
(3)
(4)
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
5.3.
Line Breaking Strictness: the line-break property
(2)
5.6.
Shaping Across Intra-word Breaks
Changes from the 13 November 2019 Working Draft
Changes from the 12 December 2018 Working Draft
(2)
Changes from the October
2013 CSS3 Text LCWD
#valdef-line-break-loose
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
(4)
(5)
(6)
(7)
(8)
#valdef-line-break-normal
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
(4)
(5)
#valdef-line-break-strict
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
(4)
(5)
#valdef-line-break-anywhere
Referenced in:
5.2.
Breaking Rules for Letters: the word-break property
5.3.
Line Breaking Strictness: the line-break property
#hyphenate
Referenced in:
5.4.
Hyphenation: the hyphens property
(2)
(3)
5.6.
Shaping Across Intra-word Breaks
#hyphenation-opportunity
Referenced in:
5.4.
Hyphenation: the hyphens property
(2)
(3)
(4)
(5)
(6)
(7)
#propdef-hyphens
Referenced in:
5.
Line Breaking and Word Boundaries
5.4.
Hyphenation: the hyphens property
(2)
(3)
Changes from the 12 December 2018 Working Draft
#propdef-overflow-wrap
Referenced in:
5.
Line Breaking and Word Boundaries
5.1.
Line Breaking Details
(2)
5.2.
Breaking Rules for Letters: the word-break property
(2)
(3)
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
5.6.
Shaping Across Intra-word Breaks
(2)
Changes from the 12 December 2018 Working Draft
(2)
Changes from the October
2013 CSS3 Text LCWD
#propdef-word-wrap
Referenced in:
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
#valdef-overflow-wrap-anywhere
Referenced in:
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
(2)
#valdef-overflow-wrap-break-word
Referenced in:
5.5.
Overflow Wrapping: the overflow-wrap/word-wrap property
#propdef-text-align
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
6.2.
Default Text Alignment: the text-align-all property
(2)
(3)
6.3.
Last Line Alignment: the text-align-last property
6.4.
Justification Method: the text-justify property
8.1.
First Line Indentation: the text-indent property
8.3.
Bidirectionality and Line Boxes
Changes from the October
2013 CSS3 Text LCWD
(2)
#valdef-text-align-start
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
8.1.
First Line Indentation: the text-indent property
#valdef-text-align-end
Referenced in:
6.1.
Text Alignment: the text-align shorthand
#valdef-text-align-center
Referenced in:
6.4.3.
Unexpandable Text
#valdef-text-align-justify
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
6.3.
Last Line Alignment: the text-align-last property
6.4.
Justification Method: the text-justify property
6.4.1.
Expanding and Compressing Text
6.4.3.
Unexpandable Text
#valdef-text-align-justify-all
Referenced in:
6.1.
Text Alignment: the text-align shorthand
#valdef-text-align-match-parent
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
6.2.
Default Text Alignment: the text-align-all property
#propdef-text-align-all
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
(3)
(4)
6.2.
Default Text Alignment: the text-align-all property
6.3.
Last Line Alignment: the text-align-last property
(2)
8.3.
Bidirectionality and Line Boxes
Changes from the October
2013 CSS3 Text LCWD
#propdef-text-align-last
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
(3)
(4)
(5)
6.2.
Default Text Alignment: the text-align-all property
6.3.
Last Line Alignment: the text-align-last property
6.4.3.
Unexpandable Text
(2)
8.3.
Bidirectionality and Line Boxes
Changes from the October
2013 CSS3 Text LCWD
(2)
#valdef-text-align-last-auto
Referenced in:
6.1.
Text Alignment: the text-align shorthand
6.2.
Default Text Alignment: the text-align-all property
#propdef-text-justify
Referenced in:
6.1.
Text Alignment: the text-align shorthand
(2)
6.4.
Justification Method: the text-justify property
(2)
(3)
(4)
(5)
6.4.1.
Expanding and Compressing Text
(2)
#valdef-text-justify-auto
Referenced in:
6.4.5.
Minimum Requirements for auto Justification
(2)
#valdef-text-justify-inter-word
Referenced in:
6.4.
Justification Method: the text-justify property
#valdef-text-justify-inter-character
Referenced in:
6.4.1.
Expanding and Compressing Text
#justification-opportunity
Referenced in:
6.1.
Text Alignment: the text-align shorthand
6.4.
Justification Method: the text-justify property
6.4.1.
Expanding and Compressing Text
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
6.4.2.
Handling Symbols and Punctuation
(2)
(3)
(4)
6.4.4.
Cursive Scripts
(2)
6.4.5.
Minimum Requirements for auto Justification
(2)
(3)
Appendix D: Scripts and Spacing
#propdef-word-spacing
Referenced in:
4.2.
Tab Character Size: the tab-size property
6.4.
Justification Method: the text-justify property
6.4.1.
Expanding and Compressing Text
(2)
7.
Spacing
7.1.
Word Spacing: the word-spacing property
7.2.
Tracking: the letter-spacing property
Appendix A:
Text Processing Order of Operations
Changes from the 12 December 2018 Working Draft
Changes from the 6 December 2018 Working Draft
Changes from the October
2013 CSS3 Text LCWD
#word-separator
Referenced in:
5.1.
Line Breaking Details
(2)
(3)
(4)
5.2.
Breaking Rules for Letters: the word-break property
6.4.
Justification Method: the text-justify property
(2)
6.4.1.
Expanding and Compressing Text
(2)
6.4.5.
Minimum Requirements for auto Justification
7.
Spacing
7.1.
Word Spacing: the word-spacing property
(2)
(3)
Changes from the 19 November 2020 Working Draft
#propdef-letter-spacing
Referenced in:
4.2.
Tab Character Size: the tab-size property
6.4.
Justification Method: the text-justify property
6.4.1.
Expanding and Compressing Text
(2)
7.
Spacing
7.2.
Tracking: the letter-spacing property
(2)
(3)
(4)
(5)
(6)
(7)
7.2.1.
Cursive Scripts
(2)
(3)
(4)
Appendix A:
Text Processing Order of Operations
Appendix D: Scripts and Spacing
Changes from the October
2013 CSS3 Text LCWD
#valdef-letter-spacing-normal
Referenced in:
7.2.
Tracking: the letter-spacing property
#propdef-text-indent
Referenced in:
8.
Edge Effects
8.1.
First Line Indentation: the text-indent property
(2)
(3)
(4)
(5)
8.3.
Bidirectionality and Line Boxes
#valdef-text-indent-each-line
Referenced in:
8.1.
First Line Indentation: the text-indent property
#valdef-text-indent-hanging
Referenced in:
8.1.
First Line Indentation: the text-indent property
(2)
#hang
Referenced in:
3.
White Space and Wrapping: the white-space property
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
(5)
(6)
(7)
(8)
5.3.
Line Breaking Strictness: the line-break property
8.2.
Hanging Glyphs
(2)
(3)
(4)
(5)
(6)
(7)
(8)
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
(3)
(4)
(5)
(6)
(7)
#hanging-glyph
Referenced in:
8.2.
Hanging Glyphs
#conditionally-hang
Referenced in:
4.1.2. Phase II: Trimming and Positioning
(2)
(3)
(4)
(5)
(6)
8.2.
Hanging Glyphs
8.2.1.
Hanging Punctuation: the hanging-punctuation property
#propdef-hanging-punctuation
Referenced in:
8.
Edge Effects
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
8.3.
Bidirectionality and Line Boxes
#valdef-hanging-punctuation-force-end
Referenced in:
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
Changes from the 12 December 2018 Working Draft
#valdef-hanging-punctuation-allow-end
Referenced in:
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
Changes from the 12 December 2018 Working Draft
#stop-or-comma
Referenced in:
8.2.1.
Hanging Punctuation: the hanging-punctuation property
(2)
#block-scripts
Referenced in:
6.4.5.
Minimum Requirements for auto Justification
(2)
#clustered-scripts
Referenced in:
6.4.5.
Minimum Requirements for auto Justification
(2)
#cursive-script
Referenced in:
6.4.4.
Cursive Scripts
(2)
7.2.1.
Cursive Scripts
(2)
Appendix D: Scripts and Spacing
Changes from the 19 November 2020 Working Draft
#unicode-east-asian-width
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
Appendix D: Scripts and Spacing
#unicode-general-category
Referenced in:
4.
White Space Processing & Control Characters
(2)
#unicode-script
Referenced in:
4.
White Space Processing & Control Characters
Appendix D: Scripts and Spacing
(2)
(3)
(4)
#writing-system-chinese
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
Appendix D: Scripts and Spacing
#writing-system-japanese
Referenced in:
5.3.
Line Breaking Strictness: the line-break property
(2)
(3)
Appendix D: Scripts and Spacing
#writing-system-korean
Referenced in:
Appendix D: Scripts and Spacing
#kana-small
Referenced in:
2.1.
Case Transforms: the text-transform property
(2)
(3)
#kana-full-size
Referenced in:
2.1.
Case Transforms: the text-transform property