CSS Multi-column Layout Module Level 1

CSS Multi-column Layout Module Level 1
CSS Multi-column Layout Module Level 1
Editor’s Draft
16 February 2026
More details about this document
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Latest published version:
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Editors:
Florian Rivoal
On behalf of Bloomberg
Rachel Andrew
Google
Former Editor:
Håkon Wium Lie
Opera Software
Suggest an Edit for this Spec:
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Abstract
This specification describes multi-column layouts in CSS, a style sheet language for the web. Using functionality described in the specification, content can be flowed into multiple columns with a gap and a rule between them.
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 is a public copy of the editors’ draft.
It is provided for discussion only and may change at any moment.
Its publication here does not imply endorsement of its contents by W3C.
Don’t cite this document other than as work in progress.
Please send feedback
by
filing issues in GitHub
(preferred),
including the spec code “css-multicol” in the title, like this:
“[css-multicol]
…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
18 August 2025 W3C Process Document
1.
Introduction
(This section is not normative.)
This module describes
multi-column layout
in CSS.
By using functionality described in this document,
style sheets can declare that the content of an element
is to be laid out in multiple columns.
Other layout methods in CSS,
when applied to a parent element,
change the display properties of the direct children.
For example if a three column grid layout is created,
the direct children of the
grid container
become
grid items
and are placed into the column tracks,
one element per cell with additional rows created as needed.
The child elements of a
multi-column container
however continue in normal flow,
that flow is arranged into a number of columns.
These columns have a flexible inline size,
and therefore respond to available space
by changing the size or number of columns displayed.
Multi-column layouts are easy to describe in CSS.
Here is a simple example:
body
column-width
12
em
In this example, the
body
element is
set to have columns at least
12em
wide. The exact number of
columns will depend on the available space.
The number of columns can also be set explicitly in the style sheet:
body
column-count
In this case, the number of columns is fixed
and the column widths will vary depending on the available width.
The shorthand
columns
property can be used to set either,
or both, properties in one declaration.
In these examples, the number of columns, the width of columns, and
both the number and width are set, respectively:
body
columns
body
columns
12
em
body
columns
12
em
Another group of properties introduced in this module describe
gaps and rules between columns.
body
column-gap
em
column-rule
thin solid black
The first declaration in the example above sets the gap
between two adjacent columns to be 1em.
Column gaps are similar to padding areas.
In the middle of the gap there will be a rule
which is described by the
column-rule
property.
The values of the
column-rule
property are similar to those of the CSS
border
properties.
Like
border
column-rule
is a shorthand property.
In this example, the shorthand
column-rule
declaration from the
above example has been expanded:
body
column-gap
em
column-rule-width
thin
column-rule-style
solid
column-rule-color
black
The
column-fill
and
column-span
properties
give style sheets a wider range of visual expressions in multi-column layouts.
In this example, columns are set to be balanced,
i.e., to have approximately the same length.
Also,
h2
elements are set to span across all columns.
div
column-fill
balance
h2
column-span
all
Tests
multicol-fill-balance-029.html
(live test)
(source)
This specification introduces ten new properties,
all of which are used in the examples above.
If all column properties have their initial value,
the layout of an element will be identical
to a multi-column layout with only one column.
Column gaps
(diagonal hatching) and
column rules
are shown in this sample rendition of a multi-column container
with padding (cross hatching).
The hatched areas are present for illustrational purposes only.
In actual implementations these areas will be determined by the background,
the second image shows a rendering of a
multi-column container
with column-rules.
A multi-column layout with the non-visible column-span and padding inside the multicol container highlighted.
The same layout as in the first image, as it would be displayed by an implementation.
1.1.
Value Definitions
This specification follows the
CSS property definition conventions
from
[CSS21]
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.
2.
The Multi-Column Model
An element whose
column-width
or
column-count
property is not
auto
establishes a
multi-column container
(or
multicol container
for short),
and therefore acts as a container for
multi-column layout
Tests
Basic multicol tests.
multicol-basic-002.html
(live test)
(source)
multicol-basic-004.html
(live test)
(source)
Tests demonstrating that auto values do not create a multicol container.
multicol-count-computed-004.xht
(live test)
(source)
Multicol properties do not inherit.
inheritance.html
(live test)
(source)
Multicol with scrolled columns.
multicol-scroll-content.html
(live test)
(source)
Multicol with zero height.
multicol-zero-height-001.xht
(live test)
(source)
multicol-zero-height-002.html
(live test)
(source)
multicol-zero-height-003.html
(live test)
(source)
In the traditional CSS box model,
the content of an element is
flowed into the content box of the corresponding element.
Multi-column layout introduces a
fragmentation context
formed of
anonymous
fragmentation containers
called
column boxes
(or
columns
for short).
These
column boxes
establish
an independent
block formatting context
into which the multi-column container’s content flows,
and form the
containing block
for its non-positioned children.
In this example, the width of the image is set with these rules:
img
display
block
width
100
Given that the column box creates a new
block formatting context
the
width
is calculated relative to the column box.
Therefore the image will not overflow the column box:
The image is constrained by the column box that it is displayed in.
Given that the column box creates a new
block formatting context
, a top margin set on the first child element of a multicol container will not collapse with the margins of the multicol container.
The margin above the first paragraph has not collapsed, leaving a
1em
margin above the first line in the multicol container.
Tests
multicol-margin-001.xht
(live test)
(source)
multicol-margin-002.xht
(live test)
(source)
multicol-margin-003.html
(live test)
(source)
multicol-margin-child-001.xht
(live test)
(source)
multicol-nested-margin-001.xht
(live test)
(source)
multicol-nested-margin-002.xht
(live test)
(source)
multicol-nested-margin-003.xht
(live test)
(source)
multicol-nested-margin-004.xht
(live test)
(source)
multicol-nested-margin-005.xht
(live test)
(source)
multicol-collapsing-001.xht
(live test)
(source)
Floats that appear inside multi-column layouts are positioned with
regard to the
column box
where the float appears.
In this example, this CSS fragment describes the presentation of the image:
img
display
block
float
right
In the HTML, the image appears after the sentence ending, "the leg of a chicken".
The image is floated inside the column box it appears in.
Content overflowing a
column box
in the
block axis
fragments
and continues in the next
column box
Note:
Column boxes, which are
anonymous boxes
do not become the
containing block
for
absolutely positioned boxes
The
position
property, which establishes a containing block for such boxes,
applies to the
multicol container
, it being the
principal box
Tests
multicol-containing-001.xht
(live test)
(source)
multicol-containing-002.xht
(live test)
(source)
multicol-containing-003.html
(live test)
(source)
multicol-contained-absolute.html
(live test)
(source)
abspos-autopos-contained-by-viewport-000.html
(live test)
(source)
abspos-autopos-contained-by-viewport-001.html
(live test)
(source)
abspos-multicol-in-second-outer-clipped.html
(live test)
(source)
In this example, the
multi-column container
has
position: relative
thus becoming the containing block.
The image is a direct child of the
multi-column container
and has
position: absolute
It takes positioning from the
multi-column container
and not from the
column box
.container
position
relative
column-count
img
position
absolute
top
20
px
left
40
px
The figure demonstrates that the absolutely positioned image is positioned by reference to the multicol container and not the column box.
Out-of-flow
descendants of a
multi-column container
do affect column balancing,
and the block-size of the
multi-column container
Tests
multicol-oof-inline-cb-001.html
(live test)
(source)
multicol-oof-inline-cb-002.html
(live test)
(source)
The column boxes are ordered
in the
inline base direction
of the multicol container
and arranged into
multicol lines
The
column width
is the length of the column box in the inline direction.
The
column height
is the length of the column box in the block direction.
All column boxes in a line have the same column width,
and all column boxes in a line have the same column height.
Tests
The following tests relate to baseline alignment of the content of columns,
though this is not defined in this specification.
baseline-000.html
(live test)
(source)
baseline-001.html
(live test)
(source)
baseline-002.html
(live test)
(source)
baseline-003.html
(live test)
(source)
baseline-004.html
(live test)
(source)
baseline-005.html
(live test)
(source)
baseline-006.html
(live test)
(source)
baseline-007.html
(live test)
(source)
baseline-008.html
(live test)
(source)
as-baseline-aligned-grid-item.html
(live test)
(source)
The following tests check the behavior of list items that are also muticol containers.
multicol-list-item-001.xht
(live test)
(source)
multicol-list-item-002.html
(live test)
(source)
multicol-list-item-003.html
(live test)
(source)
multicol-list-item-004.html
(live test)
(source)
multicol-list-item-005.html
(live test)
(source)
multicol-list-item-006.html
(live test)
(source)
multicol-list-item-007.html
(live test)
(source)
multicol-list-item-008.html
(live test)
(source)
Testing grid items inside multicol
balance-grid-001.html
(live test)
(source)
The following tests check the behavior of table elements.
multicol-table-cell-001.xht
(live test)
(source)
multicol-table-cell-height-001.xht
(live test)
(source)
multicol-table-cell-height-002.xht
(live test)
(source)
multicol-table-cell-vertical-align-001.xht
(live test)
(source)
table-cell-as-multicol.html
(live test)
(source)
table-cell-content-change-000.html
(live test)
(source)
table-cell-content-change-001.html
(live test)
(source)
table-cell-multicol-nested-001.html
(live test)
(source)
table-cell-multicol-nested-002.html
(live test)
(source)
table-cell-multicol-nested-003.html
(live test)
(source)
break-before-multicol-caption.html
(live test)
(source)
repeated-table-column.html
(live test)
(source)
table-cell-writing-mode-root.html
(live test)
(source)
balance-breakafter-before-table-section-crash.html
(live test)
(source)
balance-table-with-border-spacing.html
(live test)
(source)
balance-table-with-fractional-height-row.html
(live test)
(source)
The following tests check that paint order is correct.
float-and-block.html
(live test)
(source)
move-with-text-after-paint.html
(live test)
(source)
resize-with-text-after-paint.html
(live test)
(source)
The following tests relate to animation or transformation of multicol properties.
column-width-interpolation.html
(live test)
(source)
discrete-no-interpolation.html
(live test)
(source)
multicol-overflow-positioned-transform-001.html
(live test)
(source)
multicol-overflow-transform-001.html
(live test)
(source)
resize-multicol-with-fixed-size-children.html
(live test)
(source)
resize-multicol-with-fixed-size-children-002.html
(live test)
(source)
resize-multicol-with-fixed-size-children-003.html
(live test)
(source)
resize-in-strict-containment-nested.html
(live test)
(source)
remove-child-in-strict-containment-also-spanner.html
(live test)
(source)
composited-under-clip-under-multicol.html
(live test)
(source)
change-intrinsic-width.html
(live test)
(source)
change-fragmentainer-size-000.html
(live test)
(source)
change-fragmentainer-size-001.html
(live test)
(source)
change-fragmentainer-size-002.html
(live test)
(source)
change-fragmentainer-size-003.html
(live test)
(source)
hit-test-child-under-perspective.html
(live test)
(source)
hit-test-transformed-child.html
(live test)
(source)
Tests related to implementation bugs, not linked to specific normative text.
multicol-with-monolithic-oof-with-multicol-with-oof.html
(live test)
(source)
chrome-bug-1293905.html
(live test)
(source)
chrome-bug-1297118.html
(live test)
(source)
chrome-bug-1301281.html
(live test)
(source)
chrome-bug-1303256.html
(live test)
(source)
chrome-bug-1314866.html
(live test)
(source)
dynamic-simplified-layout-break-propagation.html
(live test)
(source)
float-multicol-crash.html
(live test)
(source)
change-abspos-width-in-second-column-crash.html
(live test)
(source)
change-out-of-flow-type-and-remove-inner-multicol-crash.html
(live test)
(source)
monolithic-oof-in-clipped-container.html
(live test)
(source)
move-linebreak-to-different-column.html
(live test)
(source)
move-newline-pre-text.html
(live test)
(source)
multicol-at-page-boundary-print.html
(live test)
(source)
multicol-block-in-inline-crash.html
(live test)
(source)
multicol-cached-consumed-bsize-crash.html
(live test)
(source)
multicol-column-change-crash.html
(live test)
(source)
multicol-dynamic-contain-crash.html
(live test)
(source)
multicol-dynamic-transform-crash.html
(live test)
(source)
multicol-floats-in-ifc.html
(live test)
(source)
multicol-parallel-flow-after-spanner-in-inline.html
(live test)
(source)
outline-move-oof-with-inline.html
(live test)
(source)
relpos-inline-with-abspos-multicol-gets-block-child.html
(live test)
(source)
size-containment-become-multicol-add-inline-child.html
(live test)
(source)
sticky-in-abs-in-sticky.html
(live test)
(source)
text-box-trim-end-and-widows.html
(live test)
(source)
vertical-rl-column-rules-wide-columns.html
(live test)
(source)
video-container-become-multicol.html
(live test)
(source)
dynamic-become-multicol-add-oof-inside-inline-crash.html
(live test)
(source)
extremely-tall-multicol-with-extremely-tall-child-crash.html
(live test)
(source)
file-control-crash.html
(live test)
(source)
img-alt-as-multicol-crash.html
(live test)
(source)
multicol-loads-indefinitely-001-crash.html
(live test)
(source)
multicol-on-broken-image-alt-text.html
(live test)
(source)
overflow-scroll-in-multicol-crash.html
(live test)
(source)
remove-block-sibling-of-inline-with-block-crash.html
(live test)
(source)
subpixel-column-progression.html
(live test)
(source)
subpixel-scroll-crash.html
(live test)
(source)
text-child-crash.html
(live test)
(source)
with-custom-layout-on-same-element-crash.https.html
(live test)
(source)
oof-in-area-001.html
(live test)
(source)
oof-in-area-002.html
(live test)
(source)
oof-in-area-003.html
(live test)
(source)
oof-in-oof-multicol-in-multicol-spanner-in-multicol.html
(live test)
(source)
oof-in-oof-multicol-in-relpos-in-oof-in-multicol-in-multicol.html
(live test)
(source)
oof-in-oof-multicol-in-relpos-spanner-in-multicol-in-relpos-multicol-in-multicol.html
(live test)
(source)
oof-in-oof-multicol-in-relpos-spanner-in-spanner-multicol-in-multicol-in-multicol.html
(live test)
(source)
oof-in-oof-multicol-in-spanner-in-multicol-in-spanner-in-nested-multicol.html
(live test)
(source)
oof-in-oof-multicol-in-spanner-in-nested-multicol.html
(live test)
(source)
oof-in-relpos-in-oof-multicol-in-oof-in-relpos-in-oof-multicol-in-multicol.html
(live test)
(source)
oof-in-relpos-in-oof-multicol-in-relpos-in-oof-multicol-in-relpos-multicol.html
(live test)
(source)
floated-input-in-inline-next-column.html
(live test)
(source)
inline-float-parallel-flow.html
(live test)
(source)
table-caption-in-clipped-overflow.html
(live test)
(source)
text-in-inline-interrupted-by-float.html
(live test)
(source)
increase-prev-sibling-height.html
(live test)
(source)
interleaved-bfc-crash.html
(live test)
(source)
relayout-fixedpos-in-abspos-in-relpos-in-nested-multicol.html
(live test)
(source)
inline-become-oof-container-make-oof-inflow.html
(live test)
(source)
multicol-dynamic-change-inside-break-inside-avoid-001.html
(live test)
(source)
multicol-dynamic-add-001.html
(live test)
(source)
multicol-dynamic-add-002.html
(live test)
(source)
multicol-dynamic-add-003.html
(live test)
(source)
multicol-dynamic-add-004.html
(live test)
(source)
scroll-width-height.tentative.html
(live test)
(source)
filter-with-abspos.html
(live test)
(source)
add-list-item-marker.html
(live test)
(source)
block-in-inline-with-abspos-after-spanner.html
(live test)
(source)
block-in-inline-with-spanner-in-overflowed-parent.html
(live test)
(source)
block-in-inline-with-spanner-in-overflowed-parent-nested-multicol.html
(live test)
(source)
first-letter-column-span-fieldset.html
(live test)
(source)
triply-nested-partial-relayout.html
(live test)
(source)
Tests related to printing and paged media as related to multicol.
auto-fill-auto-size-001-print.html
(live test)
(source)
auto-fill-auto-size-002-print.html
(live test)
(source)
multicol-height-002-print.xht
(live test)
(source)
named-page.html
(live test)
(source)
page-property-ignored.html
(live test)
(source)
Note:
In text set using a vertical writing mode,
the block direction runs horizontally.
In a vertical writing mode columns are laid out horizontally,
and the direction of the flow of blocks may be right to left, or left to right.
The
column-width
property therefore refers to the inline size of the column,
and not the physical horizontal width.
A diagram showing the different ways columns may be arranged due to writing mode.
From left to right: horizontal-tb, vertical-rl, vertical-lr.
Tests
Tests regarding vertical writing modes.
orthogonal-writing-mode-shrink-to-fit.html
(live test)
(source)
multicol-under-vertical-rl-scroll.html
(live test)
(source)
hit-test-in-vertical-rl.html
(live test)
(source)
Within each
multicol line
in the multi-column container,
adjacent column boxes are separated by a
column gap
which may contain a
column rule
All column gaps in the same multi-column container are equal.
All column rules in the same multi-column container are also equal, if they appear;
column rules only appear between columns that both have content.
In the simplest case a multicol container will contain only one line
of columns, and the height of each column will be equivalent to the
used height of the multi-column container’s content box.
However,
fragmentation
or
spanners
can split the content of the
multi-column container
into multiple
multicol lines
If the multi-column container is paginated, the height of each column is
constrained by the page and the content continues in a new line of
column boxes on the next page; a column box never splits across pages.
The same effect occurs when a
spanning element
divides the
multi-column container: the columns before the spanning element are
balanced and shortened to fit their content. Content after the
spanning element then flows into a new, subsequent line of column boxes.
A demonstration of how the spanning element divides the multicol container.
multi-column container
therefore is a regular
block container
that establishes a new
independent formatting context
whose contents consist of a series of
multicol lines
and multicol spanners.
Each
multi-column line
acts as a
block-level box
that establishes a
multi-column formatting context
for its
column boxes
and each
spanner
acts as a
block-level box
that establishes an
independent formatting context
with its type depending on its
display
value as usual.
Nested multi-column containers are allowed,
but there may be implementation-specific limits.
Tests
multicol-nested-002.xht
(live test)
(source)
multicol-nested-005.xht
(live test)
(source)
multicol-nested-006.html
(live test)
(source)
multicol-nested-007.html
(live test)
(source)
multicol-nested-008.html
(live test)
(source)
multicol-nested-009.html
(live test)
(source)
multicol-nested-010.html
(live test)
(source)
multicol-nested-011.html
(live test)
(source)
multicol-nested-012.html
(live test)
(source)
multicol-nested-013.html
(live test)
(source)
multicol-nested-014.html
(live test)
(source)
multicol-nested-015.html
(live test)
(source)
multicol-nested-016.html
(live test)
(source)
multicol-nested-017.html
(live test)
(source)
multicol-nested-018.html
(live test)
(source)
multicol-nested-019.html
(live test)
(source)
multicol-nested-020.html
(live test)
(source)
multicol-nested-021.html
(live test)
(source)
multicol-nested-022.html
(live test)
(source)
multicol-nested-023.html
(live test)
(source)
multicol-nested-024.html
(live test)
(source)
multicol-nested-025.html
(live test)
(source)
multicol-nested-026.html
(live test)
(source)
multicol-nested-027.html
(live test)
(source)
multicol-nested-028.html
(live test)
(source)
multicol-nested-029.html
(live test)
(source)
multicol-nested-030.html
(live test)
(source)
multicol-nested-031.html
(live test)
(source)
multicol-nested-032.html
(live test)
(source)
multicol-nested-033.html
(live test)
(source)
nested-as-balanced-legend.html
(live test)
(source)
nested-as-nested-balanced-legend.html
(live test)
(source)
nested-floated-multicol-with-tall-margin.html
(live test)
(source)
nested-multicol-and-float-with-tall-padding-before-float.html
(live test)
(source)
nested-multicol-and-float-with-tall-padding.html
(live test)
(source)
nested-multicol-fieldset-tall-trailing-border-freeze.html
(live test)
(source)
nested-multicol-fieldset-tall-trailing-padding.html
(live test)
(source)
nested-multicol-in-svg-foreignobject.html
(live test)
(source)
nested-multicol-nested-flex.html
(live test)
(source)
nested-multicol-with-float-between.html
(live test)
(source)
nested-oof-multicol-with-monolithic-child.html
(live test)
(source)
nested-oof-multicol-with-oof-needing-additional-columns.html
(live test)
(source)
nested-oof-multicol-with-padding.html
(live test)
(source)
nested-with-fragmented-oof-negative-top-offset.html
(live test)
(source)
nested-with-multicol-table-caption.html
(live test)
(source)
multicol-table-caption-parallel-flow-after-spanner-in-inline.html
(live test)
(source)
nested-with-multicol-table-cell.html
(live test)
(source)
nested-with-oof-inside-fixed-width.html
(live test)
(source)
nested-with-percentage-size-and-oof.html
(live test)
(source)
nested-with-tall-padding-and-oof.html
(live test)
(source)
nested-with-tall-padding.html
(live test)
(source)
oof-in-nested-line-float.html
(live test)
(source)
oof-nested-multicol-inside-oof.html
(live test)
(source)
relayout-nested-with-oof.html
(live test)
(source)
repeated-section-in-nested-table-nested-multicol.html
(live test)
(source)
repeated-table-footer-in-caption-nested-multicol.html
(live test)
(source)
nested-balanced-monolithic-multicol-crash.html
(live test)
(source)
nested-balanced-very-tall-content-crash.html
(live test)
(source)
nested-floated-shape-outside-multicol-with-monolithic-child-crash.html
(live test)
(source)
nested-with-overflowing-padding-crash.html
(live test)
(source)
triply-nested-with-fixedpos-in-abspos-crash.html
(live test)
(source)
fixed-in-nested-multicol-with-transform-container.html
(live test)
(source)
fixed-in-nested-multicol-with-viewport-container.html
(live test)
(source)
fixed-in-nested-multicol.html
(live test)
(source)
nested-after-float-clearance.html
(live test)
(source)
nested-at-outer-boundary-as-fieldset.html
(live test)
(source)
nested-at-outer-boundary-as-float.html
(live test)
(source)
nested-at-outer-boundary-as-legend.html
(live test)
(source)
nested-floated-multicol-with-monolithic-child.html
(live test)
(source)
nested-oofs-in-relative-multicol.html
(live test)
(source)
nested-past-fragmentation-line.html
(live test)
(source)
nested-with-too-tall-line.html
(live test)
(source)
oof-nested-in-single-column.html
(live test)
(source)
nested-non-auto-inline-size-offset-top.html
(live test)
(source)
fixedpos-static-pos-with-viewport-cb-001.html
(live test)
(source)
fixedpos-static-pos-with-viewport-cb-002.html
(live test)
(source)
fixedpos-static-pos-with-viewport-cb-003.html
(live test)
(source)
multicol-height-block-child-001.xht
(live test)
(source)
Note:
It is not possible to set properties/values on column boxes.
For example, the background of a certain column box cannot be set
and a column box has no concept of padding, margin or borders.
Future specifications may add additional functionality.
For example, columns of different widths and different backgrounds may be supported.
Note:
Multicol containers with column heights larger than the viewport may pose accessibility issues.
See
Accessibility Considerations
for more details.
3.
The Number and Width of Columns
Finding the number and width of columns is fundamental when laying out multi-column content.
These properties are used to set the number and width of columns:
column-count
column-width
A third property,
columns
is a shorthand property which sets both
column-width
and
column-count
Other factors, such as explicit column breaks, content, and height constraints,
may influence the actual number and width of columns.
3.1.
The Inline Size of Columns: the
column-width
property
Name:
column-width
Value:
auto

Initial:
auto
Applies to:
block containers
except
table wrapper boxes
Inherited:
no
Percentages:
N/A
Computed value:
the keyword
auto
or an absolute length
Canonical order:
per grammar
Animation type:
by computed value type
This property describes the width of columns in multicol containers.
auto
means that the column width will be determined by other properties
(e.g.,
column-count
, if it has a non-auto value).

describes the optimal column width.
The actual column width may be wider (to fill the available space),
or narrower (only if the available space is smaller than the specified column width).
Negative values are not allowed.
Used values will be clamped to a minimum of
1px
Tests
zero-column-width-computed-style.html
(live test)
(source)
zero-column-width-layout.html
(live test)
(source)
Tests
multicol-basic-003.html
(live test)
(source)
multicol-basic-008.xht
(live test)
(source)
multicol-reduce-000.xht
(live test)
(source)
multicol-width-001.xht
(live test)
(source)
multicol-width-002.xht
(live test)
(source)
multicol-width-003.xht
(live test)
(source)
multicol-width-005.html
(live test)
(source)
multicol-width-ch-001.html
(live test)
(source)
multicol-width-negative-001.xht
(live test)
(source)
multicol-width-invalid-001.xht
(live test)
(source)
multicol-width-large-001.xht
(live test)
(source)
multicol-width-large-002.xht
(live test)
(source)
multicol-inherit-003.xht
(live test)
(source)
column-width-computed.html
(live test)
(source)
column-width-invalid.html
(live test)
(source)
column-width-valid.html
(live test)
(source)
multicol-width-small-001.xht
(live test)
(source)
For example, consider this style sheet:
div
width
100
px
column-width
45
px
column-gap
column-rule
none
There is room for two
45px
wide columns inside the
100px
wide element.
In order to fill the available space
the actual column width will be increased to
50px
Also, consider this style sheet:
div
width
40
px
column-width
45
px
column-gap
column-rule
none
The available space is smaller than the specified column width
and the actual column width will therefore be decreased.
To ensure that
column-width
can be used with vertical text,
column width means the length of the line boxes inside the columns.
Note:
The reason for making
column-width
somewhat flexible
is to achieve scalable designs that can fit many screen sizes.
To set an exact column width,
the column gap and the width of the multicol container (assuming horizontal text)
must also be specified.
3.2.
The Number of Columns: the
column-count
property
Name:
column-count
Value:
auto

Initial:
auto
Applies to:
block containers
except
table wrapper boxes
Inherited:
no
Percentages:
N/A
Computed value:
specified value
Canonical order:
per grammar
Animation type:
by computed value
This property describes the number of columns of a
multicol container
auto
means that the number of columns will be determined by other properties
(e.g.,
column-width
, if it has a non-auto value).

describes the optimal number of columns into which the content of the element will be flowed.
Values must be greater than 0.
If both
column-width
and
column-count
have non-auto values,
the integer value describes the maximum number of columns.
Tests
multicol-count-001.xht
(live test)
(source)
multicol-count-002.xht
(live test)
(source)
multicol-basic-006.xht
(live test)
(source)
multicol-width-count-001.xht
(live test)
(source)
multicol-width-count-002.xht
(live test)
(source)
multicol-columns-toolong-001.xht
(live test)
(source)
multicol-count-negative-001.xht
(live test)
(source)
multicol-count-negative-002.xht
(live test)
(source)
multicol-count-non-integer-001.xht
(live test)
(source)
multicol-count-non-integer-002.xht
(live test)
(source)
multicol-count-non-integer-003.xht
(live test)
(source)
multicol-inherit-001.xht
(live test)
(source)
multicol-inherit-002.xht
(live test)
(source)
column-count-invalid.html
(live test)
(source)
column-count-valid.html
(live test)
(source)
column-count-computed.html
(live test)
(source)
column-count-interpolation.html
(live test)
(source)
large-actual-column-count.html
(live test)
(source)
with-custom-layout-on-same-element.https.html
(live test)
(source)
Example:
body
column-count
3.3.
The
column-width
and
column-count
Shorthand: The
columns
Property
Name:
columns
Value:
<'column-width'>
||
<'column-count'>
Initial:
see individual properties
Applies to:
see individual properties
Inherited:
see individual properties
Percentages:
see individual properties
Computed value:
see individual properties
Animation type:
see individual properties
Canonical order:
per grammar
This is a shorthand property for setting
column-width
and
column-count
Omitted values are set to their initial values.
Here are some valid declarations using the
columns
property:
columns
12
em
/* column-width: 12em; column-count: auto */
columns: auto
12
em
/* column-width: 12em; column-count: auto */
columns:
/* column-width: auto; column-count: 2 */
columns:
auto
/* column-width: auto; column-count: 2 */
columns: auto
/* column-width: auto; column-count: auto */
columns: auto auto
/* column-width: auto; column-count: auto */
Tests
columns-interpolation.html
(live test)
(source)
multicol-columns-001.xht
(live test)
(source)
multicol-columns-002.xht
(live test)
(source)
multicol-columns-003.xht
(live test)
(source)
multicol-columns-004.xht
(live test)
(source)
multicol-columns-005.xht
(live test)
(source)
multicol-columns-006.xht
(live test)
(source)
multicol-columns-007.xht
(live test)
(source)
multicol-columns-invalid-001.xht
(live test)
(source)
multicol-columns-invalid-002.xht
(live test)
(source)
multicol-basic-001.html
(live test)
(source)
multicol-basic-003.html
(live test)
(source)
multicol-basic-005.xht
(live test)
(source)
multicol-basic-007.xht
(live test)
(source)
columns-computed.html
(live test)
(source)
columns-invalid.html
(live test)
(source)
columns-valid.html
(live test)
(source)
3.4.
The Pseudo-algorithm
The pseudo-algorithm below determines the used values for
column-count
(N) and
column-width
(W). There is one other variable
in the pseudo-algorithm: U is the used width of the multi-column container.
Note:
The used width U of the multi-column container can depend on the element’s contents,
in which case it also depends on the computed values of the
column-count
and
column-width
properties.
This specification does not define how U is calculated.
Another module (probably the Basic Box Model
[CSS3BOX]
or the Box Sizing Module
[CSS3-SIZING]
) is expected to define this.
Tests
intrinsic-size-001.html
(live test)
(source)
intrinsic-size-002.html
(live test)
(source)
intrinsic-size-003.html
(live test)
(source)
intrinsic-size-004.html
(live test)
(source)
intrinsic-size-005.html
(live test)
(source)
as-column-flex-item.html
(live test)
(source)
intrinsic-width-change-column-count.html
(live test)
(source)
The
floor(X)
function returns the largest integer Y ≤ X.
(01) if ((column-width = auto) and (column-count = auto)) then
(02) exit; /* not a multicol container */
(03) if column-width = auto then
(04) N := column-count
(05) else if column-count = auto then
(06) N := max(1,
(07) floor((U + column-gap)/(column-width + column-gap)))
(08) else
(09) N := min(column-count, max(1,
(10) floor((U + column-gap)/(column-width + column-gap))))
And:
(11) W := max(0, (U + column-gap)/N - column-gap)
For the purpose of finding the number of auto-repeated columns,
the UA must floor the column size to a UA-specified value to avoid division by zero.
It is suggested that this floor be 1px or less.
In fragmented contexts such as in
paged media
user agents may perform this calculation on a per-fragment basis.
The used value for
column-count
is calculated without regard for explicit column breaks or constrained column heights,
while the actual value takes these into consideration.
Tests
column-count-used-001.html
(live test)
(source)
In this example, the actual column-count is higher than the used column-count
due to explicit column breaks:
div
width
40
em
columns
20
em
column-gap
break-after
column
div
one
two
three
div
The computed column-count is auto, the used column-count is 2 and the actual column-count is 3.
The actual column-count may be lower than the used column-count.
Consider this example:
div
width
80
em
height
10
em
columns
20
em
column-gap
column-fill
auto
div
foo
div
The computed column-count is auto,
the used column-count is 4,
and the actual column-count is 1.
3.5.
Stacking Context
All column boxes in a multi-column container are in the same stacking context
and the drawing order of their contents is as specified in CSS 2.1.
Column boxes do not establish new stacking contexts.
Tests
multicol-rule-stacking-001.xht
(live test)
(source)
4.
Column Gaps and Rules
Column gaps and rules are placed between columns in the same
multicol container
The length of the column gaps and column rules is equal to the column height.
Column gaps take up space.
That is, column gaps will push apart content in adjacent columns
(within the same
multicol container
).
Tests
column-rule-001.html
(live test)
(source)
column-rule-002.html
(live test)
(source)
multicol-height-001.xht
(live test)
(source)
multicol-nested-column-rule-001.xht
(live test)
(source)
multicol-nested-column-rule-002.html
(live test)
(source)
multicol-nested-column-rule-003.html
(live test)
(source)
multicol-rule-nested-balancing-001.html
(live test)
(source)
multicol-rule-nested-balancing-002.html
(live test)
(source)
multicol-rule-nested-balancing-003.html
(live test)
(source)
multicol-rule-nested-balancing-004.html
(live test)
(source)
column rule
is drawn in the middle of the
column gap
with the endpoints at opposing content edges of the
multicol container
Column rules do not take up space.
That is, the presence or thickness of a
column rule
will not alter the placement of anything else.
If a
column rule
is wider than its gap,
the adjacent column boxes will overlap the rule,
and the rule may possibly extend outside the box of the
multicol container
Column rules are painted just above the border of the
multicol container
For scrollable multicol containers,
note that while the border and background of the
multicol container
obviously aren’t scrolled,
the rules need to scroll along with the columns.
Column rules are only drawn between two columns that both have content.
Tests
Basic column rule tests
multicol-rule-003.xht
(live test)
(source)
multicol-rule-004.xht
(live test)
(source)
multicol-rule-fraction-002.xht
(live test)
(source)
If a column rule is wider than its gap, adjacent boxes overlap.
multicol-rule-001.xht
(live test)
(source)
multicol-rule-large-001.xht
(live test)
(source)
multicol-rule-large-002.xht (visual test)
(source)
Column rules are only drawn between two columns that have content.
multicol-count-computed-003.xht
(live test)
(source)
multicol-count-computed-005.xht
(live test)
(source)
broken-column-rule-1.html
(live test)
(source)
Tests for behavior of backgrounds and column rules.
multicol-breaking-000.html
(live test)
(source)
multicol-breaking-001.html
(live test)
(source)
multicol-breaking-002.html
(live test)
(source)
multicol-breaking-003.html
(live test)
(source)
multicol-breaking-004.html
(live test)
(source)
multicol-breaking-005.html
(live test)
(source)
multicol-breaking-006.html
(live test)
(source)
multicol-breaking-nobackground-000.html
(live test)
(source)
multicol-breaking-nobackground-001.html
(live test)
(source)
multicol-breaking-nobackground-002.html
(live test)
(source)
multicol-breaking-nobackground-003.html
(live test)
(source)
multicol-breaking-nobackground-004.html
(live test)
(source)
multicol-breaking-nobackground-005.html
(live test)
(source)
4.1.
Gutters Between Columns: the
column-gap
property
The
column-gap
property is defined in
[CSS3-ALIGN]
In a
multi-column formatting context
the used value of
normal
for the
column-gap
property is
1em
This ensures columns are readable when the initial values are used.
If there is a column rule between columns,
it will appear in the middle of the gap.
Tests
multicol-gap-fraction-001.xht
(live test)
(source)
multicol-gap-fraction-002.html
(live test)
(source)
multicol-gap-large-001.xht
(live test)
(source)
multicol-gap-large-002.xht
(live test)
(source)
multicol-gap-negative-001.xht
(live test)
(source)
multicol-gap-000.xht
(live test)
(source)
multicol-gap-002.xht
(live test)
(source)
multicol-gap-percentage-001.html
(live test)
(source)
multicol-gap-001.xht
(live test)
(source)
multicol-gap-003.xht
(live test)
(source)
Tests that the gap is animatable.
multicol-gap-animation-001.html
(live test)
(source)
multicol-gap-animation-002.html
(live test)
(source)
multicol-gap-animation-003.html
(live test)
(source)
4.2.
The Color of Column Rules: the
column-rule-color
property
Name:
column-rule-color
Value:

Initial:
currentcolor
Applies to:
multicol containers
Inherited:
no
Percentages:
N/A
Computed value:
computed color
Canonical order:
per grammar
Animation type:
by computed value type

Specifies the color of the
column rule
Tests
multicol-rule-color-001.xht
(live test)
(source)
multicol-rule-color-inherit-001.xht
(live test)
(source)
multicol-rule-color-inherit-002.xht
(live test)
(source)
column-rule-color-computed.html
(live test)
(source)
column-rule-color-valid.html
(live test)
(source)
column-rule-color-invalid.html
(live test)
(source)
column-rule-color-interpolation.html
(live test)
(source)
4.3.
The Style Of Column Rules: the
column-rule-style
property
Name:
column-rule-style
Value:

Initial:
none
Applies to:
multicol containers
Inherited:
no
Percentages:
N/A
Computed value:
specified keyword
Canonical order:
per grammar
Animation type:
discrete
The
column-rule-style
property sets the style of the rule between columns of an element.
The

values are interpreted as in the
collapsing border model
Tests
column-rule-style-computed.html
(live test)
(source)
column-rule-style-valid.html
(live test)
(source)
column-rule-style-invalid.html
(live test)
(source)
The
none
and
hidden
values force the used value of
column-rule-width
to be
4.4.
The Width Of Column Rules: the
column-rule-width
property
Name:
column-rule-width
Value:

Initial:
medium
Applies to:
multicol containers
Inherited:
no
Percentages:
N/A
Computed value:
absolute length,
snapped as a border width
Canonical order:
per grammar
Animation type:
by computed value type
This property sets the width of the rule between columns.
Negative values are not allowed.
Tests
multicol-rule-fraction-001.xht
(live test)
(source)
multicol-rule-fraction-003.xht
(live test)
(source)
multicol-rule-px-001.xht
(live test)
(source)
multicol-rule-percent-001.xht
(live test)
(source)
subpixel-column-rule-width.tentative.html
(live test)
(source)
column-rule-width-computed.html
(live test)
(source)
column-rule-width-invalid.html
(live test)
(source)
column-rule-width-valid.html
(live test)
(source)
column-rule-width-interpolation.html
(live test)
(source)
4.5.
Column Rule Shorthand: the
column-rule
property
Name:
column-rule
Value:
<'column-rule-width'>
||
<'column-rule-style'>
||
<'column-rule-color'>
Initial:
see individual properties
Applies to:
see individual properties
Inherited:
see individual properties
Percentages:
see individual properties
Computed value:
see individual properties
Animation type:
see individual properties
Canonical order:
per grammar
This property is a shorthand for setting
column-rule-width
column-rule-style
, and
column-rule-color
at the same place in the style sheet.
Omitted values are set to their initial values.
Tests
multicol-shorthand-001.xht
(live test)
(source)
multicol-rule-shorthand-001.xht
(live test)
(source)
multicol-rule-shorthand-2.xht
(live test)
(source)
multicol-rule-000.xht
(live test)
(source)
multicol-rule-002.xht
(live test)
(source)
multicol-rule-dashed-000.xht
(live test)
(source)
multicol-rule-dotted-000.xht
(live test)
(source)
multicol-rule-double-000.xht
(live test)
(source)
multicol-rule-outset-000.xht
(live test)
(source)
multicol-rule-none-000.xht
(live test)
(source)
multicol-rule-hidden-000.xht
(live test)
(source)
multicol-rule-inset-000.xht
(live test)
(source)
multicol-rule-groove-000.xht
(live test)
(source)
multicol-rule-ridge-000.xht
(live test)
(source)
multicol-rule-solid-000.xht
(live test)
(source)
column-rule-computed.html
(live test)
(source)
column-rule-invalid.html
(live test)
(source)
column-rule-valid.html
(live test)
(source)
column-rule-shorthand.html
(live test)
(source)
In this example, the
column rule
and the
column gap
have the same width.
Therefore, they will occupy exactly the same space.
body
column-gap
35
px
column-rule-width
35
px
column-rule-style
solid
column-rule-color
black
The column rule and column gap occupy the same space.
Tests
equal-gap-and-rule.html
(live test)
(source)
multicol-rule-samelength-001.xht
(live test)
(source)
fixed-size-child-with-overflow.html
(live test)
(source)
5.
Column Breaks
When content is laid out in multiple columns,
the user agent must determine where column breaks are placed.
The problem of breaking content into columns is similar to breaking content into pages,
which is described in CSS 2.1, section 13.3.3
[CSS21]
Three new properties are introduced to allow column breaks to be described in the same properties as page breaks:
break-before
break-after
, and
break-inside
5.1.
Controlling Fragmentation: the
break-before
break-after
break-inside
properties
break-before
break-after
, and
break-inside
are defined in
[CSS3-BREAK]
Tests
multicol-break-000.xht
(live test)
(source)
multicol-break-001.xht
(live test)
(source)
multicol-br-inside-avoidcolumn-001.xht
(live test)
(source)
moz-multicol3-column-balancing-break-inside-avoid-1.html (manual test)
(source)
6.
Spanning Columns
The
column-span
property makes it possible for an element to span across several columns.
6.1.
Spanning An Element Across Columns: the
column-span
property
Name:
column-span
Value:
none
all
Initial:
none
Applies to:
in-flow
block-level elements
Inherited:
no
Percentages:
N/A
Computed value:
specified keyword
Canonical order:
per grammar
Animation type:
discrete
Tests
column-span-invalid.html
(live test)
(source)
This property describes how many columns an element spans across. Values are:
none
The element does not span multiple columns.
Tests
multicol-span-none-001.xht
(live test)
(source)
all
The element forces a column break and is taken
out of flow
to span across all columns of the nearest multicol ancestor
in the same
block formatting context
Content in the normal flow that appears before the element
is automatically balanced across all columns
in the immediately preceding
multi-column line
before the element appears,
and any subsequent content flows into a new
multi-column line
after the element.
The element establishes an
independent formatting context
Note:
Whether the element establishes a new
formatting context
does not depend on whether the element is a descendant of a multicol or not.
When
column-span
is
all
, it always does.
This helps with robustness of designs to later revisions that remove the multicol,
or when media queries turn the multicol off in some situations.
Tests
multicol-span-000.xht
(live test)
(source)
multicol-span-all-001.xht
(live test)
(source)
multicol-span-all-003.xht
(live test)
(source)
multicol-span-all-block-sibling-003.xht
(live test)
(source)
multicol-span-all-margin-001.xht
(live test)
(source)
multicol-span-all-margin-002.xht
(live test)
(source)
multicol-span-all-margin-003.html
(live test)
(source)
multicol-span-all-margin-bottom-001.xht
(live test)
(source)
multicol-span-all-margin-nested-001.xht
(live test)
(source)
multicol-span-all-margin-nested-002.xht
(live test)
(source)
multicol-span-all-margin-nested-firstchild-001.xht
(live test)
(source)
multicol-span-float-001.xht
(live test)
(source)
multicol-span-float-002.html
(live test)
(source)
multicol-span-float-003.html
(live test)
(source)
multicol-span-float-004.html
(live test)
(source)
inline-block-and-column-span-all.html
(live test)
(source)
multicol-span-all-dynamic-remove-001.html
(live test)
(source)
multicol-span-all-dynamic-add-001.html
(live test)
(source)
multicol-span-all-dynamic-remove-002.html
(live test)
(source)
multicol-span-all-dynamic-add-002.html
(live test)
(source)
multicol-span-all-dynamic-remove-003.html
(live test)
(source)
multicol-span-all-dynamic-add-003.html
(live test)
(source)
multicol-span-all-dynamic-remove-004.html
(live test)
(source)
multicol-span-all-dynamic-add-004.html
(live test)
(source)
multicol-span-all-dynamic-add-005.html
(live test)
(source)
multicol-span-all-dynamic-remove-005.html
(live test)
(source)
multicol-span-all-dynamic-remove-006.html
(live test)
(source)
multicol-span-all-dynamic-add-006.html
(live test)
(source)
multicol-span-all-dynamic-remove-007.html
(live test)
(source)
multicol-span-all-dynamic-add-007.html
(live test)
(source)
multicol-span-all-dynamic-add-008.html
(live test)
(source)
multicol-span-all-dynamic-add-009.html
(live test)
(source)
multicol-span-all-dynamic-add-010.html
(live test)
(source)
multicol-span-all-dynamic-add-011.html
(live test)
(source)
multicol-span-all-dynamic-add-012.html
(live test)
(source)
multicol-span-all-dynamic-add-013.html
(live test)
(source)
multicol-span-all-dynamic-add-014.html
(live test)
(source)
multicol-span-all-children-height-001.html
(live test)
(source)
multicol-span-all-children-height-002.html
(live test)
(source)
multicol-span-all-children-height-003.html
(live test)
(source)
multicol-span-all-children-height-004a.html
(live test)
(source)
multicol-span-all-children-height-004b.html
(live test)
(source)
multicol-span-all-children-height-005.html
(live test)
(source)
multicol-span-all-children-height-006.html
(live test)
(source)
multicol-span-all-children-height-007.html
(live test)
(source)
multicol-span-all-children-height-008.html
(live test)
(source)
multicol-span-all-children-height-009.html
(live test)
(source)
multicol-span-all-children-height-010.html
(live test)
(source)
multicol-span-all-children-height-011.html
(live test)
(source)
multicol-span-all-children-height-012.html
(live test)
(source)
multicol-span-all-children-height-013.html
(live test)
(source)
multicol-span-all-004.html
(live test)
(source)
multicol-span-all-005.html
(live test)
(source)
multicol-span-all-006.html
(live test)
(source)
multicol-span-all-007.html
(live test)
(source)
multicol-span-all-008.html
(live test)
(source)
multicol-span-all-009.html
(live test)
(source)
multicol-span-all-010.html
(live test)
(source)
multicol-span-all-011.html
(live test)
(source)
multicol-span-all-012.html
(live test)
(source)
multicol-span-all-013.html
(live test)
(source)
multicol-span-all-014.html
(live test)
(source)
multicol-span-all-015.html
(live test)
(source)
multicol-span-all-016.html
(live test)
(source)
multicol-span-all-017.html
(live test)
(source)
multicol-span-all-018.html
(live test)
(source)
multicol-span-all-019.html
(live test)
(source)
multicol-span-all-020.html
(live test)
(source)
multicol-span-all-rule-001.html
(live test)
(source)
multicol-span-all-rule-002.html
(live test)
(source)
multicol-span-all-button-001.html
(live test)
(source)
multicol-span-all-button-002.html
(live test)
(source)
multicol-span-all-button-003.html
(live test)
(source)
multicol-span-all-fieldset-001.html
(live test)
(source)
multicol-span-all-fieldset-002.html
(live test)
(source)
multicol-span-all-fieldset-003.html
(live test)
(source)
multicol-span-all-restyle-001.html
(live test)
(source)
multicol-span-all-restyle-002.html
(live test)
(source)
multicol-span-all-restyle-003.html
(live test)
(source)
multicol-span-all-restyle-004.html
(live test)
(source)
multicol-span-all-list-item-001.html
(live test)
(source)
multicol-span-all-list-item-002.html
(live test)
(source)
multicol-span-auto-size-in-vertical-writing-mode-001.html
(live test)
(source)
multicol-span-auto-size-in-vertical-writing-mode-002.html
(live test)
(source)
float-with-line-after-spanner.html
(live test)
(source)
parallel-flow-after-spanner-001.html
(live test)
(source)
parallel-flow-after-spanner-002.html
(live test)
(source)
margin-and-break-before-child-spanner.html
(live test)
(source)
multicol-width-004.html
(live test)
(source)
An element that spans more than one column is called a
multi-column spanning element
and the box it creates is called a
multi-column spanner
The
containing block
of the
spanner
is the
multicol container
itself.
Consequently, in cases where the spanner itself does not establish
containing block
for
absolutely positioned boxes
inside the spanner,
their
containing block chain
skips directly to the
multicol container
(skipping any ancestors between the
spanner
and the
multicol container
).
Although the spanner is taken
out-of-flow
this does not affect the
painting order
[CSS21]
of the spanning element.
In this example, an
h2
element has been added to the sample document after the sixth sentence
(i.e., after the words "the leg of a").
This styling applies:
h2
column-span
all
background
silver
By setting
column-span
to
all
all content that appears before the
h2
element
is shown above the
h2
element.
The h2 element is set to column-span: all
Note that because the spanner splits the
multi-column line
it also interrupts any
column rules
(which are only drawn between
columns
in a
multi-column line
).
A spanning element may be lower than the first level of descendants
as long as they are part of the same
formatting context
and there is nothing between the spanning element and
multicol container
that establishes a containing block for fixed position descendants.
In this example, the element with
column-span: all
is inside an element with
transform: rotate(90deg)
The transform establishes a containing block for fixed position descendents,
therefore a spanner will not be created.
article
section
div
class
"spanner"
Attempted spanner
div
section
article
article
columns
section
transform
rotate
90
deg
);
.spanner
column-span
all
background
silver
Tests
fixed-in-multicol-with-transform-container.html
(live test)
(source)
change-transform-in-nested.html
(live test)
(source)
change-transform-in-second-column.html
(live test)
(source)
change-transform.html
(live test)
(source)
If the fragment before the spanner is empty, nothing special happens;
the top margin/border/padding is above the spanning element, as an empty
fragment
In this example the
multicol container
is the
article
element.
Inside this parent is a paragraph and then a section element.
The section contains an
h2
heading set to
all
this spans all three columns while the containing section remains inside the column boxes.
The
h2
is the first child of the section.
This means that the margin,
border (shown in red in the diagram)
and padding on this section appear before the spanning
h2
as an empty fragment.
article
...
section
h2
An h2 element
h2
...
section
article
section
border
px
solid red
margin-top
65
px
padding-top
20
px
h2
column-span
all
background
silver
The
h2
element is set to
column-span: all
the section has a red border and top padding and margin
Tests
spanner-fragmentation-000.html
(live test)
(source)
spanner-fragmentation-001.html
(live test)
(source)
spanner-fragmentation-002.html
(live test)
(source)
spanner-fragmentation-003.html
(live test)
(source)
spanner-fragmentation-004.html
(live test)
(source)
spanner-fragmentation-005.html
(live test)
(source)
spanner-fragmentation-006.html
(live test)
(source)
spanner-fragmentation-007.html
(live test)
(source)
spanner-fragmentation-008.html
(live test)
(source)
spanner-fragmentation-009.html
(live test)
(source)
spanner-fragmentation-010.html
(live test)
(source)
spanner-fragmentation-011.html
(live test)
(source)
spanner-fragmentation-012.html
(live test)
(source)
A spanning element takes up more space than the element would take up otherwise.
When space is limited, it may be impossible to find room for the spanning element.
In these cases, user agents may treat the element as if
none
had been specified on this property.
In this example, the
h2
element appears later in the content,
and the height of the multicol container is constrained.
Therefore, the
h2
element appears in the overflow
and there is not room to make the element spanning.
As a result, the element appears as if
column-span: none
was specified.
The h2 element is in an overflow column and appears as if column-span none is specified
This example is similar to the previous example,
except that the H2 element appears naturally in the last column.
Still, there is not enough room to make the element spanning.
The h2 element is in the final column and appears as if column-span none is specified
Tests
multicol-span-all-002.xht
(live test)
(source)
In fragmented contexts spanning elements are honored in all fragments.
In this example, we are in
paged media
and the first three paragraphs have column breaks after them.
A spanning
H2
element appears after the fourth paragraph.
This would appear on the first page
This would appear on the second page
Spanners are block-level boxes
therefore the margins of two adjacent spanners will collapse with each other.
The margins of two spanners separated only by an absolutely positioned item will collapse with each other,
as absolutely positioned items do not create column boxes.
As column boxes establish a new
block formatting context
margins on elements inside a column box will not collapse with the margin of a spanner.
Tests
non-adjacent-spanners-000.html
(live test)
(source)
non-adjacent-spanners-001.html
(live test)
(source)
Spanners establish new
formatting contexts
, but their margins can be changed by their surroundings.
In this example, two spanners naturally end up at the top of a page.
The top margin of the first spanner is truncated due to adjoining an unforced break.
The margins between the two spanners collapse with each other.
However, the bottom margin of the second spanner does not collapse with the top margin of the subsequent element.
h2
margin
16
px
column-span
all
background
silver
margin-top
16
px
Margins collapse between two spanning elements, but not the bottom margin of a spanner and top margin of next element.
Tests
Additional tests relating to spanners.
abspos-in-multicol-with-spanner-crash.html
(live test)
(source)
body-becomes-spanner-html-becomes-vertical-rl.html
(live test)
(source)
fit-content-with-spanner-and-auto-scrollbar-sibling.html
(live test)
(source)
float-becomes-non-float-spanner-surprises-inside.html
(live test)
(source)
float-becomes-spanner.html
(live test)
(source)
float-becomes-spanner-remove-child.html
(live test)
(source)
float-cannot-be-spanner.html
(live test)
(source)
multicol-floats-after-column-span-crash.html
(live test)
(source)
negative-margin-on-column-spanner.html
(live test)
(source)
nested-spanner-with-negative-margin.html
(live test)
(source)
oof-becomes-spanner.html
(live test)
(source)
oof-in-additional-column-before-spanner.html
(live test)
(source)
oof-in-spanner-in-relpos-in-multicol-in-relpos-multicol-001.html
(live test)
(source)
oof-in-spanner-in-relpos-in-multicol-in-relpos-multicol-002.html
(live test)
(source)
relpos-spanner-with-spanner-child-becomes-regular.html
(live test)
(source)
remove-spanner-after-spanner-in-inline-before-inline.html
(live test)
(source)
remove-spanner-in-table-caption-nested-multicol.html
(live test)
(source)
remove-transform-descendant-becomes-spanner-remove-spanner-child.html
(live test)
(source)
restricted-height-bottom-border-overflow-and-spanner.html
(live test)
(source)
scrollable-spanner-in-nested.html
(live test)
(source)
spanner-after-parallel-flow.html
(live test)
(source)
spanner-in-inline-after-very-tall-content-001.html
(live test)
(source)
spanner-in-inline-after-very-tall-content-002.html
(live test)
(source)
spanner-in-overflowed-container-before-float.html
(live test)
(source)
spanner-in-relpos-in-abspos-multicol-in-multicol.html
(live test)
(source)
nested-with-tall-padding-and-spanner-and-content.html
(live test)
(source)
specified-height-with-just-spanner-and-oof.html
(live test)
(source)
trailing-parent-padding-between-spanners.html
(live test)
(source)
table-caption-change-descendant-display-type.html
(live test)
(source)
table-caption-inline-block-remove-child.html
(live test)
(source)
remove-block-beside-spanner-in-inline-crash.html
(live test)
(source)
remove-inline-with-block-beside-spanners-crash.html
(live test)
(source)
remove-spanner-beside-spanner-in-inline-crash.html
(live test)
(source)
remove-transform-descendant-becomes-spanner.html
(live test)
(source)
spanning-legend-000-crash.html
(live test)
(source)
spanning-legend-001-crash.html
(live test)
(source)
toggle-spanner-float-crash.html
(live test)
(source)
abspos-after-spanner-static-pos.html
(live test)
(source)
abspos-after-spanner.html
(live test)
(source)
abspos-containing-block-outside-spanner.html
(live test)
(source)
change-transform-in-spanner.html
(live test)
(source)
nested-with-padding-and-spanner.html
(live test)
(source)
orthogonal-writing-mode-spanner.html
(live test)
(source)
remove-inline-with-block-beside-spanners.html
(live test)
(source)
replaced-content-spanner-auto-width.html
(live test)
(source)
spanner-in-child-after-parallel-flow-001.html
(live test)
(source)
spanner-in-child-after-parallel-flow-002.html
(live test)
(source)
spanner-in-child-after-parallel-flow-003.html
(live test)
(source)
spanner-in-child-after-parallel-flow-004.html
(live test)
(source)
spanner-in-opacity.html
(live test)
(source)
going-out-of-flow-after-spanner.html
(live test)
(source)
inline-with-spanner-in-overflowed-container-before-multicol-float.html
(live test)
(source)
spanner-in-overflowed-clipped-container.html
(live test)
(source)
spanner-in-overflowed-container-before-inline-content.html
(live test)
(source)
spanner-inside-inline-in-overflowed-container.html
(live test)
(source)
column-span-valid.html
(live test)
(source)
column-span-computed.html
(live test)
(source)
getclientrects-000.html
(live test)
(source)
getclientrects-001.html
(live test)
(source)
7.
Filling Columns
There are two strategies for filling columns:
columns can either be balanced, or not.
If columns are balanced, user agents should try to minimize variations in column height,
while honoring forced breaks,
widows
and
orphans
and other properties that may affect column heights.
If columns are not balanced, they are filled sequentially;
some columns may end up partially filled, or with no content at all.
7.1.
Column Balancing: the
column-fill
property
Name:
column-fill
Value:
auto
balance
balance-all
Initial:
balance
Applies to:
multicol containers
Inherited:
no
Percentages:
N/A
Computed value:
specified keyword
Canonical order:
per grammar
Animation type:
discrete
This property specifies whether content
in a
multi-column line
that does
not
immediately precede a
spanner
is balanced across columns or not.
Tests
always-balancing-before-column-span.html
(live test)
(source)
no-balancing-after-column-span.html
(live test)
(source)
The values are:
balance
Balance content equally between columns, as far as possible.
In fragmented contexts, only the last fragment is balanced.
Tests
multicol-fill-000.xht
(live test)
(source)
multicol-fill-001.xht
(live test)
(source)
column-fill-invalid.html
(live test)
(source)
column-fill-valid.html
(live test)
(source)
column-fill-computed.html
(live test)
(source)
column-fill-balance-orthog-block-001.html
(live test)
(source)
column-balancing-paged-001-print.html
(live test)
(source)
multicol-fill-balance-001.xht
(live test)
(source)
multicol-fill-balance-002.html
(live test)
(source)
multicol-fill-balance-003.html
(live test)
(source)
multicol-fill-balance-004.html
(live test)
(source)
multicol-fill-balance-005.html
(live test)
(source)
multicol-fill-balance-006.html
(live test)
(source)
multicol-fill-balance-007.html
(live test)
(source)
multicol-fill-balance-008.html
(live test)
(source)
multicol-fill-balance-009.html
(live test)
(source)
multicol-fill-balance-010.html
(live test)
(source)
multicol-fill-balance-011.html
(live test)
(source)
multicol-fill-balance-012.html
(live test)
(source)
multicol-fill-balance-013.html
(live test)
(source)
multicol-fill-balance-014.html
(live test)
(source)
multicol-fill-balance-015.html
(live test)
(source)
multicol-fill-balance-016.html
(live test)
(source)
multicol-fill-balance-018.html
(live test)
(source)
multicol-fill-balance-019.html
(live test)
(source)
multicol-fill-balance-020.html
(live test)
(source)
multicol-fill-balance-021.html
(live test)
(source)
multicol-fill-balance-022.html
(live test)
(source)
multicol-fill-balance-023.html
(live test)
(source)
multicol-fill-balance-024.html
(live test)
(source)
multicol-fill-balance-025.html
(live test)
(source)
multicol-fill-balance-026.html
(live test)
(source)
multicol-fill-balance-027.html
(live test)
(source)
multicol-fill-balance-028.html
(live test)
(source)
multicol-fill-balance-030.html
(live test)
(source)
multicol-fill-balance-031.html
(live test)
(source)
multicol-fill-balance-032.html
(live test)
(source)
multicol-fill-balance-033.html
(live test)
(source)
multicol-fill-balance-034.html
(live test)
(source)
multicol-fill-balance-035.html
(live test)
(source)
multicol-fill-balance-036.html
(live test)
(source)
multicol-fill-balance-037.html
(live test)
(source)
multicol-fill-balance-038.html
(live test)
(source)
multicol-fill-balance-039.html
(live test)
(source)
multicol-fill-balance-nested-000.html
(live test)
(source)
balance-all
Balance content equally between columns, as far as possible.
In fragmented contexts, all fragments are balanced.
auto
fill columns sequentially
Tests
multicol-fill-auto-001.xht
(live test)
(source)
multicol-fill-auto-002.xht
(live test)
(source)
multicol-fill-auto-003.xht
(live test)
(source)
multicol-fill-auto-004.html
(live test)
(source)
multicol-fill-auto-block-children-001.xht
(live test)
(source)
multicol-fill-auto-block-children-002.xht
(live test)
(source)
multicol-fill-auto-block-children-003.html
(live test)
(source)
columnfill-auto-max-height-001.html
(live test)
(source)
columnfill-auto-max-height-002.html
(live test)
(source)
columnfill-auto-max-height-003.html
(live test)
(source)
In continuous contexts, this property does not have any effect when there are overflow columns.
In this example, an article only has one short paragraph which fits on three lines.
The three lines are displayed in three different
columns due to column balancing.
article
width
60
em
height
auto
columns
column-fill
balance
Three lines displayed in three columns due to column balancing.
In this example, column balancing is turned off, and the article has a height:
article
width
60
em
height
em
columns
column-fill
auto
As a result, the first column is filled with all content:
No balancing so the whole text is shown in one paragraph.
In this example, an article has two paragraphs:
first a long one,
then a shorter one.
This code is applied:
article
width
60
em
height
auto
columns
column-fill
balance
break-after
column
The shortest column height possible contains five lines of text.
After the column height has been established, columns are filled sequentially.
As a result, the third column is as high as the first two columns,
while the last column ends up being significantly shorter.
Once column height is established, columns are filled sequentially.
article
width
60
em
height
auto
columns
column-fill
balance
In this example, an article starts with an unbreakable figure which sets the column height.
Subsequent content is filled sequentially into the remaining columns:
Column height is established by the figure.
Tests
Tests relating to column balancing in combination with out-of-flow elements.
column-balancing-with-span-and-oof-001.html
(live test)
(source)
column-balancing-with-span-and-oof-002.html
(live test)
(source)
forced-break-in-oof-in-column-balancing-nested.html
(live test)
(source)
forced-break-in-oof-in-column-balancing.html
(live test)
(source)
Other tests relating to balancing
balance-extremely-tall-monolithic-content-crash.html
(live test)
(source)
column-balancing-with-overflow-auto-crash.html
(live test)
(source)
balance-break-avoidance-000.html
(live test)
(source)
balance-break-avoidance-001.html
(live test)
(source)
balance-break-avoidance-002.html
(live test)
(source)
balance-grid-container.html
(live test)
(source)
balance-orphans-widows-000.html
(live test)
(source)
balance-with-forced-break.html
(live test)
(source)
balancing-flex-item-trailing-margin-freeze.html
(live test)
(source)
balancing-tall-borders-freeze.html
(live test)
(source)
8.
Overflow
8.1.
Overflow Inside Multicol Containers
Except for cases where this would cause a column break,
content that extends outside column boxes
visibly overflows and is not clipped to the
column box
Note:
See
§ 5 Column Breaks
for column breaks
and
§ 8.2 Pagination and Overflow Outside Multicol Containers
for whether it is clipped to the multi-column container’s content box.
In this example, the image is wider than the column:
Content visibly overflows and is not clipped to the column box.
Tests
multicol-block-no-clip-001.xht
(live test)
(source)
multicol-block-no-clip-002.xht
(live test)
(source)
multicol-clip-001.xht
(live test)
(source)
multicol-clip-002.xht
(live test)
(source)
multicol-clip-scrolled-content-001.html
(live test)
(source)
multicol-overflow-clip-auto-sized.html
(live test)
(source)
multicol-overflow-clip-positioned.html
(live test)
(source)
multicol-overflow-clip.html
(live test)
(source)
relative-child-overflowing-column-gap.html
(live test)
(source)
relative-child-overflowing-container.html
(live test)
(source)
8.2.
Pagination and Overflow Outside Multicol Containers
Content and column rules that extend outside column boxes at
the edges of the multi-column container are clipped according to the
overflow
property.
A multicol container can have more columns than it has room for due to:
a declaration that constrains the column height
(e.g., using
height
or
max-height
).
In this case, additional column boxes are created in the inline direction
the size of the page.
In this case, additional column boxes are moved to the next page(s).
explicit column breaks.
In this case, additional column boxes are created in the inline direction for continuous contexts
and additional column boxes are moved to the next fragment(s) for fragmented media.
Tests
multicol-overflow-000.xht
(live test)
(source)
multicol-overflowing-001.xht
(live test)
(source)
Tests to check that a scrollable container isn't split across multiple columns.
overflow-unsplittable-001.html
(live test)
(source)
overflow-unsplittable-002.html
(live test)
(source)
overflow-unsplittable-003.html
(live test)
(source)
Columns that appear outside the multicol container in continuous contexts
are called
overflow columns
Overflow columns can affect the height of the multicol container.
In this example, the height of the multi-column container has been constrained to a maximum height.
Also, the style sheet specifies that overflowing content should be visible:
div
max-height
em
overflow
visible
As a result, the number of columns is increased.
An overflow column is created in the inline direction.
In continuous contexts overflow columns can affect the height of the multicol container.
In this example a column appears in the overflow which has four lines of text.
The multicol container is made tall enough to accommodate this column.
The final column is an overflow column yet is taller than the others.
The container is tall enough for this column.
In fragmented contexts, the overflow content goes into columns in subsequent fragments.
Given the same content as in example 31
and a page box that only has room for five lines of formatted text,
this would appear on the first page:
The first three paragraphs appear on page one.
Assuming column balancing, this would appear on the second page:
The overflow column is moved onto page two.
In this example, explicit column breaks are generated after paragraphs:
break-after
column
As a result, the number of columns increases and the extra columns are added in the inline direction:
An overflow column is created in the inline direction.
In
paged media
, extra columns are shown on the next page.
Given the same code as the previous example,
the last paragraph appears on the second page.
This would appear on the first page:
The first three paragraphs appear on page one.
This would appear on the second page:
The overflow column is moved onto page two.
Due to column balancing, the last paragraph is split across three columns.
Appendix B. Changes
This appendix is
informative
Changes from the
Candidate Recommendation (CR) of 16 May 2024
Removed the special case of
column-rule-width
having a computed value of
when
column-rule-style
is
none
or
hidden
Issue 11494
Changes from the
Candidate Recommendation (CR) of 12 October 2021
Added the text "and there is nothing between the spanning element and
multicol container
that establishes a containing block for fixed position descendants."
Resolved 9 Mar 2022
Changes from the
Working Draft (WD) of 12 February 2021
Added the text "Out-of-flow descendants of a multi-column container do affect column balancing,
and the block-size of the multi-column container."
Resolved 12 May 2021
Added the text, "The margins of two spanners separated only by an absolutely positioned item will collapse with each other,
as absolutely positioned items do not create column boxes."
Resolved 12 May 2021
Adds an accessibility considerations section.
Request from APA after review.
Adds a note and example to make clear the manner in which columns are laid out in vertical writing modes.
Request from i18n WG after review.
Changes from the
Working Draft (WD) of 15 October 2019
Added the text "The spanner becomes the containing block for absolutely positioned boxes inside the spanner where the spanning element establishes a containing block, otherwise the containing block chain goes to the multicol container.".
Resolved 23 Oct 2020
Adding the text "This property specifies whether content
in a multi-column line that does
not
immediately precede a spanner
is balanced across columns or not."
Resolved 29 April 2020
Changes from the
Working Draft (WD) of 28 May 2018
Removed the non-normative text
"However, as described below, setting both the width and number of columns rarely makes sense." Editorial 16 Sep 2019,
issue 4291
Added the paragraph, "Spanners are block-level boxes
therefore the margins of two adjacent spanners will collapse with each other.
As column boxes establish a new
block formatting context
margins on elements inside a column box will not collapse with the margin of a spanner."
Resolved 22 Oct 2018
, see also the resolution for
issue 2582
Clarified the spec to explain that a spanning element is taken out-of-flow, leaving a forced break. Added the paragraph, "A spanning element is taken out-of-flow, leaving a forced break. This does not affect the painting order of the spanning element."
Resolved 28 Feb 2019
Moved the definition of the
column-gap
property to
[CSS3-ALIGN]
and added a paragraph detailing the specifics of
column-gap
in multicol:
"In a multi-column formatting context the used value of normal for the column-gap property is 1em. This ensures columns are readable when the initial values are used. If there is a column rule between columns, it will appear in the middle of the gap."
Resolved 4 June 2019.
Reworded the section
The multi-column model
, based on input from Morten Stenshorne in
issue 2203
Removed the at-risk marker from the length-percentage value for
column-gap
Resolved 4 June 2019.
Updated the introduction to remove mention of the benefits of multicol over using tables for layout and instead refer to the unique characteristics of multicol. Editorial change referenced in
issue 3654
Changed the sentence added in the pseudo-algorithm section after the 7 Jan 2016 resolution, to refer to
columns
and not
tracks
as tracks are not defined in this specification. Resolved
13 March 2019
Changes and clarifications to the SVG images used in the specification.
Changed syntax to use bracketed range notation to reflect the prose restrictions on negative/non-zero values.
Changes from the
Working Draft (WD) of 5 October 2017
Changed references to paged media to refer to fragmented contexts. Resolved
12 Apr 2018
Changed a line regarding the
column-fill
property:
In continuous media, this property does not have any effect in
overflow columns.
To:
In continuous media, this property does not have any effect when there are overflow columns.
Resolved: 12 Apr 2018
Add a line of text plus an example to show that overflow columns can affect the multicol container height.
Resolved: 12 Apr 2018
Replaced the HTML mock-up examples with SVG versions, as the examples were unclear.
Issue 1087
Changed the value of normal for column-gap to be 1em, rather than a UA-specified length with a suggestion of 1em.
Resolved: 4 Apr 2018
Clarified that negative values are not allowed for column-width, and that while 0 may be specified, used values will be clamped to a minimum of 1px.
Resolved: 14 Mar 2018
Clarified that where there is a spanning element content is automatically balanced across all columns in the immediately preceding column row before the element appears.
Resolved: 9 Nov 2017
Added clarification plus an additional example that spanning elements may be lower the first level of descendants, and that in the case of margins, borders and padding on the element containing the spanning, this would be drawn above the spanner.
Resolved: 8 Nov 2017
Changed the sentence
Column rules are painted in the inline content layer, but below all inline content inside the multicol element.
to
Column rules are painted just above the border of the multicol element. For scrollable multicol elements, note that while the border and background of the multicol element obviously aren’t scrolled, the rules need to scroll along with the columns.
Resolved: 7 Nov 2017
Under section The Multi-column Model, removed two sentences
That is, column boxes behave like block-level, table cell, and inline-block boxes as per CSS 2.1, section 10.1, item 2 CSS21. However, column boxes do not establish block container boxes for elements with
position: fixed or position: absolute
. These were replaced with a clarification about the principal box and a new example showing how abspos elements refer to the multicol container.
Resolved: 7 Nov 2017
Removed the sentence "To indicate where column breaks should (or should not) appear, new keyword values are introduced." and following example (Example 7 in the WD published
5 Oct 2017
) as the multicol specification no longer introduces these properties.
Editorial
Changed how we reference the element we have applied multicol to from multi-column or multicol
element
to multi-column or multicol
container
Resolved: 22 November 2017
Removed the example which stated "If a tall image is moved to a column on the next page to find room for it, its natural column may be left empty. If so, the column is still considered to have content for the purpose of deciding if the column rule should be drawn."
Resolved: 7 September 2017
Changes from the
Candidate Recommendation (CR) of 12 April 2011
Added July 2016 resolution to change the track size floor to a required UA-specified value, consistent with the CSS Grid spec.
Resolved: 7 Jan 2016
Remove the restriction about overflow columns only being in continuous media in the statement that
column-fill
has no effect on overflow columns.
Resolved: September 2013
Added keyword balance-all and examples to demonstrate how this should work.
Resolved: September 2013
The pseudo-algorithm has been revised on a number of occasions.
Latest change Feb 2013
Clarified that properties
columns
column-width
column-count
"apply to block containers".
Ref: Feb 2013
Breaking properties have been moved from this specification to the
CSS Fragmentation Module
Change to
column-fill
wording to clarify that
column-fill
is honored before page breaks.
Ref: Jan 2012
Amended example and text to clarify what happens with margin collapsing and spanning elements.
Ref: Oct 2013
Clarification that
column-rule-width
does not alter the size or placement of columns.
Ref: Sep 2013
Added that each column spanning element establishes a separate BFC margins between them collapse.
Ref: Dec 2011
Column rules are painted in the inline content layer, but below all inline content inside the multicol.
Ref: Feb 2013
Clarify that
column-span
causes the element to establish a formatting context even if it is not in a multicol.
Column spanners do not always establish a
block
formatting context.
Allow
column-gap
to accept

instead of just

column-width
and
column-count
applies to
block containers
except
table wrapper boxes
Content that overflows columns is not clipped.
Privacy Considerations
Multicol introduces no new privacy leaks.
Security Considerations
Multicol introduces no new security considerations.
Accessibility Considerations
Setting container height and line length can pose challenges for people with visual or cognitive disabilities.
See
WCAG Success Criterion 1.4.10 Reflow
and
WCAG 1.4.8 Visual Presentation
to understand user needs.
Acknowledgments
This document is based on several older proposals and comments on older proposals.
Contributors include:
Alex Mogilevsky,
Andy Clarke,
Anton Prowse,
Bert Bos,
Björn Höhrmann,
Cédric Savarese,
Chris Lilley,
Chris Wilson,
Daniel Glazman and
Dave Raggett,
David Hyatt,
David Singer,
David Woolley,
Elika Etemad,
Giovanni Campagna,
Ian Hickson.
Joost de Valk,
Kevin Lawver,
L. David Baron,
Markus Mielke,
Melinda Grant,
Michael Day,
Morten Stenshorne,
Øyvind Stenhaug,
Peter Linss,
Peter-Paul Koch,
Robert O’Callahan,
Robert Stevahn,
Sergey Genkin,
Shelby Moore,
Steve Zilles,
Sylvain Galineau,
Tantek Çelik,
Till Halbach
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.
Tests
Tests relating to the content of this specification
may be documented in “Tests” blocks like this one.
Any such block is non-normative.
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.
Index
Terms defined by this specification
all
, in § 6.1
auto
value for column-count
, in § 3.2
value for column-fill
, in § 7.1
value for column-width
, in § 3.1
balance
, in § 7.1
balance-all
, in § 7.1

, in § 4.2
column
, in § 2
column box
, in § 2
column-count
, in § 3.2
column-fill
, in § 7.1
column gap
, in § 2
column height
, in § 2
column rule
, in § 2
column-rule
, in § 4.5
column-rule-color
, in § 4.2
column-rule-style
, in § 4.3
column-rule-width
, in § 4.4
columns
, in § 3.3
column-span
, in § 6.1
column width
, in § 2
column-width
, in § 3.1

, in § 3.2

, in § 3.1
multicol container
, in § 2
multi-col line
, in § 2
multicol line
, in § 2
multi-column container
, in § 2
multi-column formatting context
, in § 2
multi-column layout
, in § 1
multi-column line
, in § 2
multi-column spanner
, in § 6.1
multi-column spanning element
, in § 6.1
none
, in § 6.1
overflow columns
, in § 8.2
spanner
, in § 6.1
spanning element
, in § 6.1
Terms defined by reference
[CSS-BACKGROUNDS-3]
defines the following terms:


border
hidden
none
[CSS-BREAK-4]
defines the following terms:
fragment
fragmentation
fragmentation container
fragmentation context
widows
[CSS-COLOR-5]
defines the following terms:

[CSS-DISPLAY-3]
defines the following terms:
display
[CSS-DISPLAY-4]
defines the following terms:
anonymous box
block container
block formatting context
block-level box
containing block
containing block chain
formatting context
in-flow
independent formatting context
out of flow
out-of-flow
principal box
[CSS-GRID-2]
defines the following terms:
grid container
grid item
[CSS-OVERFLOW-3]
defines the following terms:
overflow
[CSS-POSITION-3]
defines the following terms:
absolutely positioned box
position
[CSS-TABLES-3]
defines the following terms:
table wrapper box
[CSS-TRANSFORMS-1]
defines the following terms:
transform
[CSS-VALUES-4]
defines the following terms:



CSS-wide keywords
snap as a border width
||
[CSS-WRITING-MODES-4]
defines the following terms:
block axis
inline base direction
[CSS3-ALIGN]
defines the following terms:
column-gap
normal
[CSS3-BREAK]
defines the following terms:
break-after
break-before
break-inside
orphans
[CSS3-SIZING]
defines the following terms:
height
max-height
width
[MEDIAQUERIES-5]
defines the following terms:
paged media
References
Normative References
[CSS-BACKGROUNDS-3]
Elika Etemad; Brad Kemper.
CSS Backgrounds and Borders Module Level 3
. URL:
[CSS-BREAK-4]
Rossen Atanassov; Elika Etemad.
CSS Fragmentation Module Level 4
. URL:
[CSS-COLOR-5]
Chris Lilley; Una Kravets; Lea Verou.
CSS Color Module Level 5
. URL:
[CSS-DISPLAY-3]
Elika Etemad; Tab Atkins Jr..
CSS Display Module Level 3
. URL:
[CSS-DISPLAY-4]
Elika Etemad; Tab Atkins Jr..
CSS Display Module Level 4
. URL:
[CSS-GRID-2]
Tab Atkins Jr.; et al.
CSS Grid Layout Module Level 2
. URL:
[CSS-OVERFLOW-3]
Elika Etemad; Florian Rivoal.
CSS Overflow Module Level 3
. URL:
[CSS-POSITION-3]
Elika Etemad; Tab Atkins Jr..
CSS Positioned Layout Module Level 3
. URL:
[CSS-TABLES-3]
Keith Cirkel.
CSS Table Module Level 3
. URL:
[CSS-VALUES-3]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 3
. URL:
[CSS-VALUES-4]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 4
. URL:
[CSS-WRITING-MODES-4]
Elika Etemad; Koji Ishii.
CSS Writing Modes Level 4
. URL:
[CSS21]
Bert Bos; et al.
Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification
. URL:
[CSS3-ALIGN]
Elika Etemad; Tab Atkins Jr..
CSS Box Alignment Module Level 3
. URL:
[CSS3-BREAK]
Rossen Atanassov; Elika Etemad.
CSS Fragmentation Module Level 3
. URL:
[CSS3-SIZING]
Tab Atkins Jr.; Elika Etemad.
CSS Box Sizing Module Level 3
. URL:
[MEDIAQUERIES-5]
Tab Atkins Jr.; et al.
Media Queries Level 5
. URL:
[RFC2119]
S. Bradner.
Key words for use in RFCs to Indicate Requirement Levels
. March 1997. Best Current Practice. URL:
Non-Normative References
[CSS-TRANSFORMS-1]
Simon Fraser; et al.
CSS Transforms Module Level 1
. URL:
[CSS3BOX]
Elika Etemad.
CSS Box Model Module Level 3
. URL:
Property Index
Name
Value
Initial
Applies to
Inh.
%ages
Anim­ation type
Canonical order
Com­puted value
column-count
auto |
auto
block containers except table wrapper boxes
no
N/A
by computed value
per grammar
specified value
column-fill
auto | balance | balance-all
balance
multicol containers
no
N/A
discrete
per grammar
specified keyword
column-rule
<'column-rule-width'> || <'column-rule-style'> || <'column-rule-color'>
see individual properties
see individual properties
see individual properties
see individual properties
see individual properties
per grammar
see individual properties
column-rule-color

currentcolor
multicol containers
no
N/A
by computed value type
per grammar
computed color
column-rule-style

none
multicol containers
no
N/A
discrete
per grammar
specified keyword
column-rule-width

medium
multicol containers
no
N/A
by computed value type
per grammar
absolute length, snapped as a border width
column-span
none | all
none
in-flow block-level elements
no
N/A
discrete
per grammar
specified keyword
column-width
auto |
auto
block containers except table wrapper boxes
no
N/A
by computed value type
per grammar
the keyword auto or an absolute length
columns
<'column-width'> || <'column-count'>
see individual properties
see individual properties
see individual properties
see individual properties
see individual properties
per grammar
see individual properties
MDN
break-after
In all current engines.
Firefox
65+
Safari
10+
Chrome
50+
Opera
37+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile
37+
break-before
In all current engines.
Firefox
65+
Safari
10+
Chrome
50+
Opera
37+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile
37+
break-inside
In all current engines.
Firefox
65+
Safari
10+
Chrome
50+
Opera
37+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile
37+
MDN
column-count
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-fill
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile
MDN
column-gap
In all current engines.
Firefox
1.5+
Safari
3+
Chrome
1+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile
11.1+
MDN
column-rule-color
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-rule-style
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-rule-width
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-rule
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-span
In all current engines.
Firefox
71+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
column-width
In all current engines.
Firefox
50+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
50+
iOS Safari
9+
Chrome for Android
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
columns
In all current engines.
Firefox
52+
Safari
9+
Chrome
50+
Opera
11.1+
Edge
79+
Edge (Legacy)
12+
IE
10+
Firefox for Android
52+
iOS Safari
9+
Chrome for Android
50+
Android WebView
50+
Samsung Internet
Opera Mobile
11.1+
MDN
widows
Firefox
None
Safari
1.3+
Chrome
25+
Opera
9.2+
Edge
79+
Edge (Legacy)
12+
IE
8+
Firefox for Android
iOS Safari
Chrome for Android
Android WebView
Samsung Internet
Opera Mobile