CSS Basic User Interface Module Level 3 (CSS3 UI)

CSS Basic User Interface Module Level 3 (CSS3 UI)
CSS Basic User Interface Module Level 3 (CSS3 UI)
W3C Recommendation
7 April 2026
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Tantek Çelik
Mozilla
tantek@cs.stanford.edu
Florian Rivoal
On behalf of Bloomberg
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Abstract
This specification describes user interface related
properties and values that are proposed for CSS level 3
to style HTML and XML (including XHTML).
It includes and extends user interface related features from the
properties and values of CSS level 2 revision 1.
It uses various
properties and values to style basic user interface elements in a document.
CSS
is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, etc.
Status of this document
This section describes the status of this document at the time of its publication.
A list of current W3C publications
and the latest revision of this technical report
can be found in the
W3C standards and drafts index.
This document was published by the
CSS Working Group
as a Recommendation using the
Recommendation track
It includes
candidate corrections.
A W3C Recommendation is a specification that, after extensive consensus-building, is endorsed by
W3C
and its Members, and has commitments from Working Group members to
royalty-free licensing
for implementations.
Candidate corrections are marked in the document.
W3C recommends the wide deployment of this specification as a standard for the Web.
Please send feedback
by
filing issues in GitHub
(preferred),
including the spec code “css-ui” in the title, like this:
“[css-ui]
…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
This document was produced by a group operating under the
W3C Patent Policy
W3C maintains a
public list of any patent disclosures
made in connection with the deliverables of the group;
that page also includes instructions for disclosing a patent.
An individual who has actual knowledge of a patent that the individual believes
contains
Essential Claim(s)
must disclose the information in accordance with
section 6 of the W3C Patent Policy
1.
Introduction
This module describes CSS properties which enable authors
to style user interface related properties and values.
Section 2.1 of CSS1
[CSS1]
and
Chapter 18 of CSS2
[CSS2]
introduced several user interface related properties and values.
User Interface for CSS3 (16 February 2000)
introduced several new user interface related features.
This specification incorporates, extends, and supersedes them.
1.1.
Purpose
The purpose of this specification is to achieve the following objectives:
Extend the user interface features in CSS2.1.
Provide additional CSS mechanisms to augment or replace other
dynamic presentation related features in HTML.
2.
Module Interactions
This document defines new features not present in earlier specifications.
In addition, it replaces and supersedes the following:
Section 18.1
section 18.4
and Information on the stacking of outlines defined in
Appendix E
of Cascading Style Sheets, level 2, revision 1
[CSS2]
User Interface for CSS3 (16 February 2000)
2.1.
Value Definitions
This specification follows the
CSS property definition conventions
from
[CSS2]
using the
value definition syntax
from
[CSS-VALUES-3]
Value types not defined in this specification are defined in CSS Values & Units
[CSS-VALUES-3]
Combination with other CSS modules may expand the definitions of these value types.
In addition to the property-specific values listed in their definitions,
all properties defined in this specification
also accept the
CSS-wide keywords
as their property value.
For readability they have not been repeated explicitly.
Candidate Correction 3:
[CSS-CASCADE-4]
and
[WEB-ANIMATIONS-1]
have refined how to define properties,
with precise definitions for the concepts underlying
animation type
and
computed value
The definitions of properties throughout this specification
are updated to use this terminology.
In many cases, this is arguably editorial,
but in some it defines previously unclear or ambiguous behavior.
3.
Box Model addition
3.1.
Changing the Box Model: the
box-sizing
property
Name:
box-sizing
Value:
content-box
border-box
Initial:
content-box
Applies to:
all elements that accept width or height
Inherited:
no
Percentages:
N/A
Computed value:
specified value
Canonical order:
per grammar
Animation type:
discrete
content-box
This is the behavior of width and height as specified by CSS2.1.
The specified width and height (and respective min/max properties)
apply to the width and height respectively of the content box of the element.
The padding and border of the element are laid out
and drawn outside the specified width and height.
border-box
Length and percentages values for width and height (and respective min/max properties)
on this element determine the border box of the element.
That is, any padding or border specified on the element
is laid out and drawn inside this specified width and height.
The content width and height are calculated
by subtracting the border and padding widths of the respective sides
from the specified
width
and
height
properties.
As the content width and height
cannot be negative
[CSS2]
, section 10.2),
this computation is floored at 0.
Used values, as exposed for instance through getComputedStyle(), also refer to the border box.
Note:
This is the behavior of width and height as commonly implemented
by legacy HTML user agents for replaced elements and input elements.
Note:
In contrast to the length and percentage values,
the
auto
value of the
width
and
height
properties
(as well as other keyword values introduced by later specifications,
unless otherwise specified)
is not influenced by the
box-sizing
property,
and always sets the size of the content box.
The following terms, whose definitions vary based on the computed value of
box-sizing
are introduced:
box-sizing: content-box
box-sizing: border-box
min inner width
min-width
max(0,
min-width
padding-left
padding-right
border-left-width
border-right-width
max inner width
max-width
max(0,
max-width
padding-left
padding-right
border-left-width
border-right-width
min inner height
min-height
max(0,
min-height
padding-top
padding-bottom
border-top-width
border-bottom-width
max inner height
max-height
max(0,
max-height
padding-top
padding-bottom
border-top-width
border-bottom-width
The
Visual formatting model details
of
[CSS2]
are written assuming
box-sizing: content-box
. The following disambiguations are made to clarify the behavior for all values of
box-sizing
In
10.3.3
, the second
width
in the following phrase is to be interpreted as
content width
If
width
is not
auto
and
border-left-width
padding-left
width
+ [...]
In
10.3.7
width
is to be interpreted as
content width
in the following equation:
left
margin-left
border-left-width
padding-left
width
+ [...]
In
10.4
width
height
min-width
max-width
min-height
and
max-height
are respectively to be interpreted as
content width
content height
min inner width
max inner width
min inner height
and
max inner height
in the following phrases:
The tentative used width is calculated [...]
If the tentative used width is greater than
max-width
, the rules above are applied again, but this time using the computed value of
max-width
as the computed value for
width
If the resulting width is smaller than
min-width
, the rules above are applied again, but this time using the value of
min-width
as the computed value for
width
Select from the table the resolved height and width values for the appropriate constraint violation. Take the max-width and max-height as max(min, max) so that min ≤ max holds true. In this table w and h stand for the results of the width and height computations [...]
All instances of these words in the table
Then apply the rules under "Calculating widths and margins" above, as if
width
were computed as this value.
In
10.6.4
height
is to be interpreted as
content height
in the following equation:
top
margin-top
border-top-width
padding-top
height
+ [...]
In
10.7
width
height
min-height
and
max-height
are respectively to be interpreted as
content width
content height
min inner height
and
max inner height
in the following phrases:
The tentative used height is calculated [...]
If this tentative height is greater than
max-height
, the rules above are applied again, but this time using the value of
max-height
as the computed value for
height
If the resulting height is smaller than
min-height
, the rules above are applied again, but this time using the value of
min-height
as the computed value for
height
[...] use the algorithm under Minimum and maximum widths above to find the used width and height. Then apply the rules under "Computing heights and margins" above, using the resulting width and height as if they were the computed values.
Example(s):
Using box-sizing to evenly share space
This example uses box-sizing to evenly horizontally split
two divs with fixed size borders inside a div container,
which would otherwise require additional markup.
sample CSS:
div.container
width
38
em
border
em
solid black
div.split
box-sizing
border-box
width
50
border
em
silver ridge
float
left
sample HTML fragment:
div
class
"container"
div
class
"split"
This div occupies the left half.
div
div
class
"split"
This div occupies the right half.
div
div
demonstration of sample CSS and HTML:
This div should occupy the left half.
This div should occupy the right half.
The two divs above should appear side by side, each (including borders) 50% of the content width of their container. If instead they are stacked one on top of the other then your browser does not support
box-sizing
4.
Outline properties
At times, style sheet authors may want to create outlines around
visual objects such as buttons, active form fields, image maps, etc.,
to make them stand out. Outlines differ from borders in the following
ways:
Outlines do not take up space.
Outlines may be non-rectangular.
UAs often render outlines on elements in the :focus state.
The outline properties control the style of these dynamic outlines.
The stacking of the rendering of these outlines is explicitly left up to implementations to provide a better user experience per platform. This supersedes the stacking of outlines as defined in
Appendix E of CSS 2.1
[CSS2]
Keyboard users,
in particular people with disabilities
who may not be able to interact with the page in any other fashion,
depend on the outline being visible
on elements in the :focus state,
thus authors must not make the outline invisible on such elements
without making sure an alternative highlighting mechanism is provided.
The rendering of applying transforms to outlines is left explicitly undefined in CSS3-UI.
4.1.
Outlines Shorthand: the
outline
property
Name:
outline
Value:
<'outline-color'>
||
<'outline-style'>
||
<'outline-width'>
Initial:
see individual properties
Applies to:
all elements
Inherited:
no
Percentages:
N/A
Computed value:
see individual properties
Animation type:
see individual properties
Canonical order:
per grammar
4.2.
Outline Thickness: the
outline-width
property
Candidate Correction 2:
[CSS-VALUES-4]
has introduced the concept of
snapping as a border width
as a type of rounding applied to some lengths
to ensure reasonable visual display.
Define
outline-width
to use this concept,
for consistency with other border-like things.
Candidate Correction 4:
Remove the special-case
where
outline-width
computes to 0
based on
outline-style: none
keeping things consistent with
a similar change being applied to
column-rule-width
and
border-width
(See
Issue 11494
.)
Name:
outline-width
Value:

Initial:
medium
Applies to:
all elements
Inherited:
no
Percentages:
N/A
Computed value:
absolute length
snapped as a border width
if the outline style is
none
Canonical order:
per grammar
Animation type:
length
by computed value
4.3.
Outline Patterns: the
outline-style
property
Name:
outline-style
Value:
auto
border-style
Initial:
none
Applies to:
all elements
Inherited:
no
Percentages:
N/A
Computed value:
as specified
Canonical order:
per grammar
Animation type:
discrete
4.4.
Outline Colors: the
outline-color
property
Name:
outline-color
Value:

invert
Initial:
invert
Applies to:
all elements
Inherited:
no
Percentages:
N/A
Computed value:
The computed value for
invert
is
invert
the computed value of
currentColor
is
currentColor
(See
currentcolor
);
see the
color
property for other

values.
Canonical order:
per grammar
Animation type:
color
by computed value
The outline created with the outline properties is drawn "over" a box,
i.e., the outline is always on top,
and doesn’t influence the position or size of the box,
or of any other boxes.
Therefore, displaying or suppressing outlines does not cause reflow.
Outlines may be non-rectangular.
For example, if the element is broken across several lines,
the outline should be an outline or minimum set of outlines
that encloses all the element’s boxes.
Each part of the outline should be fully connected
rather than open on some sides
(as borders on inline elements are when lines are broken).
The parts of the outline are not required to be rectangular.
To the extent that the outline follows the
border edge
it should follow the
border-radius
curve.
The position of the outline may be affected by descendant boxes.
User agents should use an algorithm for determining
the outline that encloses a region appropriate
for conveying the concept of focus to the user.
Note:
This specification does not define the exact position or shape of the outline, but it is typically drawn immediately outside the border box.
The
outline-width
property accepts the same values as
border-width
CSS Backgrounds 3
§ 3.3 Line Thickness: the border-width properties
).
The
outline-style
property accepts the same values as
border-style
CSS Backgrounds 3
§ 3.2 Line Patterns: the border-style properties
),
except that
hidden
is not a legal outline style.
In addition, in CSS3,
outline-style
accepts the value
auto
The
auto
value permits the user agent
to render a custom outline style,
typically a style which is either a user interface default for the platform,
or perhaps a style that is richer
than can be described in detail in CSS,
e.g. a rounded edge outline with semi-translucent outer pixels
that appears to glow.
As such, this specification does not define how the
outline-color
is incorporated or used (if at all) when rendering
auto
style outlines.
User agents may treat
auto
as
solid
The
outline-color
property
accepts all colors, as well as the keyword
invert
Invert
is expected to perform a color inversion on the pixels on the screen.
This is a common trick to ensure the focus border is visible,
regardless of color background.
Conformant UAs may ignore the
invert
value
on platforms that do not support color inversion of the pixels on the screen.
If the UA does not support the
invert
value
then it must reject that value at parse-time, and
the initial value of the
outline-color
property
is the
currentColor
keyword.
The
outline
property is a shorthand property,
and sets all three of
outline-style
outline-width
and
outline-color
Note:
The outline is the same on all sides.
In contrast to borders,
there are no
outline-top
or
outline-left
etc. properties.
This specification does not define how multiple overlapping outlines are drawn,
or how outlines are drawn for boxes that are partially obscured behind other elements.
Example(s):
Here’s an example of drawing a thick outline around a BUTTON element:
button
outline
thick solid
Graphical user interfaces may use outlines around elements
to tell the user which element on the page has the focus.
These outlines are in addition to any borders,
and switching outlines on and off should not cause the document to reflow.
The focus is the subject of user interaction in a document
(e.g. for entering text or selecting a button).
Example(s):
For example, to draw a thick black line around an element when it has the focus,
and a thick red line when it is active,
the following rules can be used:
:focus
outline
thick solid black
:active
outline
thick solid red
Note:
Since the outline does not affect formatting
(i.e., no space is left for it in the box model),
it may well overlap other elements on the page.
4.5.
Offsetting the Outline: the
outline-offset
property
By default, the outline is drawn starting just outside the
border edge
However, it is possible to offset the outline and draw it beyond the
border edge
Name:
outline-offset
Value:

Initial:
Applies to:
all elements
Inherited:
no
Percentages:
N/A
Computed value:

value in absolute units (px or physical).
absolute length
Canonical order:
per grammar
Animation type:
length
by computed value
If the computed value of
outline-offset
is anything other than 0,
then the outline is outset from the
border edge
by that amount.
Example(s):
For example,
to leave 2 pixels of space between a focus outline
and the element that has the focus or is active,
the following rule can be used:
:focus
:active
outline-offset
px
Negative values must cause the outline
to shrink into the border box.
Both the height and the width of outside of the shape
drawn by the outline should not become smaller
than twice the computed value of the
outline-width
property,
to make sure that an outline can be rendered
even with large negative values.
User agents should apply this constraint
independently in each dimension.
If the outline is drawn as multiple disconnected shapes,
this constraint applies to each shape separately.
5.
Resizing & Overflow
CSS2.1 provides a mechanism for controlling the appearance of a scrolling mechanism
(e.g. scrollbars)
on block container elements.
This specification adds to that a mechanism for controlling
user resizability of elements as well as the ability to specify text overflow behavior.
5.1.
Resizing Boxes: the
resize
property
The
resize
property allows the author
to specify whether or not an element is resizable by the user,
and if so, along which axis/axes.
Candidate Correction 1:
Now that
overflow: visible
is no longer the only value
of the
overflow
property which doesn’t cause the element to become a
scroll container
adjust what elements to which the
resize
property applies to
to match the original intent,
rather than the literal text.
Name:
resize
Value:
none
both
horizontal
vertical
Initial:
none
Applies to:
elements
with
overflow
other than visible,
that are
scroll containers
and optionally replaced elements such as images, videos, and iframes
Inherited:
no
Percentages:
N/A
Computed value:
as
specified
keyword
Canonical order:
per grammar
Animation type:
discrete
none
The UA does not present a resizing mechanism on the element,
and the user is given no direct manipulation mechanism to resize the element.
both
The UA presents a bidirectional resizing mechanism
to allow the user to adjust both the height and the width of the element.
horizontal
The UA presents a unidirectional horizontal resizing mechanism
to allow the user to adjust only the width of the element.
vertical
The UA presents a unidirectional vertical resizing mechanism
to allow the user to adjust only the height of the element.
Currently it is possible to control the appearance of the scrolling mechanism (if any)
on an element using the
overflow
property
(e.g.
overflow
scroll
vs.
overflow
hidden
etc.).
The purpose of the
resize
property
is to allow control over the appearance and function of the resizing mechanism
(e.g. a resize box or widget) on the element.
Note:
The resizing mechanism is NOT the same as the scrolling mechanism,
nor is it related to any UA mechanism for zooming.
The scrolling mechanism allows the user
to determine which portion of the contents of an element is shown.
The resizing mechanism allows the user
to determine the size of the element.
The
resize
property applies to elements
whose computed
overflow
value
is something other than
visible
that are
scroll containers
UAs may also apply it,
regardless of the value of the
overflow
property,
to:
Replaced elements representing images or videos, such as
img
video
picture
svg
object
, or
canvas
The
iframe
element.
The effect of the
resize
property on generated content is undefined. Implementations should not apply the
resize
property to generated content.
Note:
the
resize
property may apply to generated content in the future if there is implementation of the
CSSPseudoElement
interface (See
[css-pseudo-4]
).
When an element is resized by the user,
the user agent sets
the
width
and
height
properties
to px unit length values of the size indicated by the user,
in the element’s
style attribute
DOM,
replacing existing property declaration(s), if any,
without
!important
, if any.
If an element is resized in only one dimension,
only the corresponding property is set, not both.
The precise direction of resizing
(i.e. altering the top left of the element or altering the bottom right)
may depend on a number of CSS layout factors
including whether the element is absolutely positioned,
whether it is positioned using the
right
and
bottom
properties,
whether the language of the element is right-to-left etc.
The UA should consider the direction of resizing
(as determined by CSS layout),
as well as platform conventions and constraints when deciding
how to convey the resizing mechanism to the user.
The user agent must allow the user to resize the element
with no other constraints than what is imposed by
min-width
max-width
min-height
, and
max-height
Note:
There may be situations where user attempts to resize an element
appear to be overridden or ignored, e.g. because of
!important
cascading declarations that supersede
that element’s
style attribute
width
and
height
properties in the DOM.
Changes to the computed value of an element’s
resize
property
do not reset changes to the
style attribute
made due to
user resizing of that element.
Example(s):
For example,
to make iframes scrollable
and
resizable,
the following rule can be used:
iframe
object
type^=
"text/"
],
object
type$=
"+xml"
],
object
type=
"application/xml"
overflow
auto
resize
both
5.2.
Overflow Ellipsis: the
text-overflow
property
Name:
text-overflow
Value:
clip
ellipsis
Initial:
clip
Applies to:
block containers
Inherited:
no
Percentages:
N/A
Computed value:
as
specified
keyword
Canonical order:
per grammar
Animation type:
discrete
This property specifies rendering when inline content overflows
its
end
line box edge
in the inline progression direction of its block container element ("the block")
that has
overflow
other than
visible
Text can overflow for example when it is prevented from wrapping
(e.g. due to
white-space
nowrap
or a single word is too long to fit).
Values have the following meanings:
clip
Clip inline content that overflows its block container element. Characters may be only partially rendered.
ellipsis
Render an ellipsis character (U+2026)
to represent clipped inline content.
Implementations may substitute a more language, script, or writing-mode appropriate
ellipsis character,
or three dots "..." if the ellipsis character is unavailable.
The term "character" is used in this property definition
for better readability and means "grapheme cluster"
[UAX29]
for implementation purposes.
For the ellipsis value
implementations must hide characters and
atomic inline-level elements
at the
end
edge of the line as necessary to fit the ellipsis, and
place the ellipsis immediately adjacent
to the
end
edge of the remaining inline content.
The first character or
atomic inline-level element
on a line
must be clipped rather than ellipsed.
Bidi ellipsis examples
These examples demonstrate which characters get hidden
to make room for the ellipsis in a bidi situation:
those visually at the end edge of the line.
Sample CSS:
div
font-family
monospace
white-space
pre
overflow
hidden
width
ch
text-overflow
ellipsis
Sample HTML fragments, renderings, and your browser:
HTML
Reference rendering
Your Browser
div
שלום 123456
div
123456 ם…
שלום 123456
div
dir
rtl
שלום 123456
div
…456 שלום
שלום 123456
ellipsing details
Ellipsing only affects rendering and must not affect layout
nor dispatching of pointer events:
The UA should dispatch any pointer event on the ellipsis to the elided element,
as if
text-overflow
had been
none
The ellipsis is styled and baseline-aligned according to
the block.
Ellipsing occurs after relative positioning and other graphical transformations.
If there is insufficient space for the ellipsis,
then clip the rendering of the ellipsis itself
(on the same side that neutral characters on the line
would have otherwise been clipped with the
text-overflow:clip
value).
user interaction with ellipsis
When the user is interacting with content
(e.g. editing, selecting, scrolling),
the user agent may treat
text-overflow: ellipsis
as
text-overflow: clip
Selecting the ellipsis should select the ellipsed text.
If all of the ellipsed text is selected,
UAs should show selection of the ellipsis.
Behavior of partially-selected ellipsed text is up to the UA.
Example(s):
text-overflow examples
These examples demonstrate setting the text-overflow of a block container element
that has text which overflows its dimensions:
sample CSS for a div:
div
font-family
Helvetica
sans-serif
line-height
1.1
width
3.1
em
padding
.2
em
border
solid
.1
em
black
margin
em
sample HTML fragments, renderings, and your browser:
HTML
sample rendering
your browser
div
CSS IS AWESOME, YES
div
First, a box with text drawing outside of it.
CSS IS AWESOME, YES
div
style
text-overflow:clip;
overflow:hidden"
CSS IS AWESOME, YES
div
Second, a similar box with the text clipped outside the box.
CSS IS AWESOME, YES
div
style
text-overflow:ellipsis;
overflow:hidden"
CSS IS AWESOME, YES
div
Third, a similar box with an ellipsis representing the clipped text.
CSS IS AWESOME, YES
div
style
text-overflow:ellipsis;
overflow:hidden"
NESTED
PARAGRAPH
WON'T ELLIPSE.
div
Fourth, a box with a nested paragraph demonstrating anonymous block boxes equivalency and non-inheritance into a nested element.
NESTED
PARAGRAPH
WON’T ELLIPSE.
Note:
the side of the line that the ellipsis is placed depends on the
direction
of the block.
E.g. an overflow hidden right-to-left
direction
rtl
block clips inline content on the
left
side,
thus would place a text-overflow ellipsis on the
left
to represent that clipped content.
ellipsis interaction with scrolling interfaces
This section applies to elements with text-overflow other than
text-overflow:clip
(non-clip text-overflow)
and overflow:scroll.
When an element with non-clip text-overflow has overflow of scroll
in the inline progression dimension of the text,
and the browser provides a mechanism for scrolling
(e.g. a scrollbar on the element,
or a touch interface to swipe-scroll, etc.),
there are additional implementation details that provide a better user experience:
When an element is scrolled (e.g. by the user, DOM manipulation),
more of the element’s content is shown.
The value of text-overflow should not affect
whether more of the element’s content is shown or not.
If a non-clip text-overflow is set,
then as more content is scrolled into view,
implementations should show whatever additional content fits,
only truncating content which would otherwise be clipped
(or is necessary to make room for the ellipsis/string),
until the element is scrolled far enough
to display the edge of the content
at which point that content should be displayed
rather than an ellipsis/string.
Example(s):
This example uses text-overflow on an element with overflow scroll
to demonstrate the above described behavior.
sample CSS:
div.crawlbar
text-overflow
ellipsis
height
em
overflow
scroll
white-space
nowrap
width
15
em
border
em
solid black
sample HTML fragment:
div
class
"crawlbar"
CSS is awesome, especially when you can scroll
to see extra text instead of just
having it overlap other text by default.
div
demonstration of sample CSS and HTML:
CSS is awesome, especially when you can scroll
to see extra text instead of just
having it overlap other text by default.
While the content is being scrolled, implementations may adjust their rendering of ellipses (e.g. align to the box edge rather than line edge).
6.
Pointing Devices and Keyboards
6.1.
Pointer interaction
6.1.1.
Styling the Cursor: the
cursor
property
Name:
cursor
Value:


Initial:
auto
Applies to:
all elements
Inherited:
yes
Percentages:
N/A
Computed value:
as specified, except with any relative URLs converted to absolute
Canonical order:
per grammar
Animation type:
discrete
This property specifies the type of cursor to be displayed for the pointing device
when the cursor’s hotspot is within the element’s
border edge
Note:
As per
CSS Backgrounds 3
§ 4.1 Curve Radii: the border-radius properties
, the
border edge
is affected by
border-radius
In the case of overlapping elements,
which element determines the type of cursor
is based on hit testing:
the element determining the cursor
is the one that would receive a click
initiated from this position.
Note:
The specifics of hit testing
are out of scope of this specification.
Hit testing will hopefully be defined
in a future revision of CSS or HTML.
User agents may ignore the cursor property over native user-agent controls such as scrollbars, resizers, or other native UI widgets e.g. those that may be used inside some user agent specific implementations of form elements.
User agents may also ignore the cursor property
and display a cursor of their choice
to indicate various states of the UA’s user interface,
such as a busy cursor when the page is not responding,
or a text cursor when the user is performing text selection.
Note:
[HTML]
defines
special handling of image maps
for the
cursor
property.
Values have the following meanings:

The first (optional) component of the
cursor
property
is a list of image-based cursors.
If the user agent cannot handle the first cursor of a list of cursors,
it must attempt to handle the second, etc.
If the user agent cannot handle any of these author-defined cursors,
it must use the keyword-based cursor at the end of the list.

has the following syntax:



{2}
The user agent retrieves the cursor from the resource designated by the URL.
Conforming user agents may, instead of

, support

which is a superset.
The UA must support the following image file formats:
PNG, as defined in
[PNG]
SVG, as defined in
[SVG11]
, in
secure static mode
[SVG2]
, if it has a
natural size
any other non-animated image file format that they support
for

in other properties,
such as the
background-image
property
In addition, the UA should support the following image file formats:
SVG, as defined in
[SVG11]
, in
secure animated mode
[SVG2]
, if it has a
natural size
any other animated image file format that they support
for

in other properties,
such as the
background-image
property
The UA may also support additional file formats, including SVG, as defined in
[SVG11]
, in secure static mode or secure animated mode
[SVG2]
, even if it does not have a
natural size
Note:
The CSS Working group initially intended support for all SVG,
naturally sized or not.
Support for non-naturally sized SVG was downgraded from mandatory to optional due
to lack of implementations.
Note:
At the time of writing this specification (spring 2015),
the only file formats supported for cursors in common desktop browsers are
the .ico and .cur file formats, as designed by Microsoft.
For compatibility with legacy content,
UAs are encouraged to support these,
even though the lack of an open specification
makes it impossible to have a normative requirement
about these formats.
Some information on these formats can be found
on Wikipedia
The
default object size
for cursor images is
a UA-defined size that should be based on
the size of a typical cursor on the UA’s operating system.
The
concrete object size
is determined using
the
default sizing algorithm
If an operating system is
incapable
of rendering a cursor above a given size,
cursors larger than that size must be shrunk to within
the OS-supported size bounds,
while maintaining the cursor image’s
natural aspect ratio
, if any.
The optional pair of

values
give the X and Y coordinates
of the exact position within the image which is the pointer position (i.e., the hotspot),
as offsets from the left/top of the image.
Note:
This specification does not define
how the coordinate systems of the various types of

are established,
and defers these definitions to
[CSS4-IMAGES]
If the values are omitted,
then the natural hotspot defined inside the image resource itself is used.
If it has no natural hotspot,
the top left corner of the image is used,
as if
0 0
were provided.
If the X or Y coordinates of the hotspot
(whether specified explicitly or taken from the image)
fall outside of the cursor image,
they must be clamped (independently) to fit.

The mandatory

keyword
specifies a predefined cursor to use,
or the
fallback
cursor to be used
if

s were provided
and none of them can be successfully used.
See
§ 6.1.1.1 Predefined Cursors
for the full set of

keywords
and their meanings.
Example: cursor fallback
Here is an example of using several cursor values.
:link
:visited
cursor
url
example.svg#linkcursor
),
url
hyper.cur
),
url
hyper.png
pointer
This example sets the cursor on all hyperlinks (whether visited or not)
to an external
SVG cursor
[SVG11]
, section 16.8.3).
User agents that don’t support SVG cursors would simply skip
to the next value and attempt to use the "hyper.cur" cursor.
If that cursor format was also not supported,
the UA could attempt to use the "hyper.png" cursor with the explicit hotspot.
Finally if the UA does not support any of those image cursor formats, the UA would skip to the last value
and render the
pointer
cursor.
6.1.1.1.
Predefined Cursors
The

production encompasses a broad selection of predefined cursors,
present on most operating systems.
Its syntax is:

= auto
default
none
context-menu
help
pointer
progress
wait
cell
crosshair
text
vertical-text
alias
copy
move
no-drop
not-allowed
grab
grabbing
e-resize
n-resize
ne-resize
nw-resize
s-resize
se-resize
sw-resize
w-resize
ew-resize
ns-resize
nesw-resize
nwse-resize
col-resize
row-resize
all-scroll
zoom-in
zoom-out
The

keywords have the following meanings
and likely renderings:
general purpose cursors
auto
The UA determines the cursor to display based on the current context:
auto
behaves as
text
over selectable text or editable elements,
and
default
otherwise.
default
The platform-dependent default cursor. Often rendered as an arrow.
none
No cursor is rendered for the element.
links and status cursors
context-menu
A context menu is available for the object under the cursor.
Often rendered as an arrow with a small menu-like graphic next to it.
help
Help is available for the object under the cursor.
Often rendered as a question mark or a balloon.
pointer
The cursor is a pointer that indicates a link.
progress
A progress indicator. The program is performing some processing,
but is different from
wait
in that the user may still interact
with the program. Often rendered as a spinning beach ball,
or an arrow with a watch or hourglass.
wait
Indicates that the program is busy and the user should wait.
Often rendered as a watch or hourglass.
selection cursors
cell
Indicates that a cell or set of cells may be selected. Often rendered as a thick plus-sign with a dot in the middle.
crosshair
A simple crosshair (e.g., short line segments resembling a "+" sign).
Often used to indicate a two dimensional bitmap selection mode.
text
Indicates text that may be selected. Often rendered as a vertical I-beam.
User agents may automatically display a horizontal I-beam/cursor
(e.g. same as the
vertical-text
keyword)
for vertical text, or for that matter,
any angle of I-beam/cursor for text that is rendered at any particular angle.
vertical-text
Indicates vertical-text that may be selected. Often rendered as a horizontal I-beam.
drag and drop cursors
alias
Indicates an alias of/shortcut to something is to be created.
Often rendered as an arrow with a small curved arrow next to it.
copy
Indicates something is to be copied.
Often rendered as an arrow with a small plus sign next to it.
move
Indicates something is to be moved.
no-drop
Indicates that the dragged item cannot be dropped at the current cursor location.
Often rendered as a hand or pointer with a small circle with a line through it.
not-allowed
Indicates that the requested action will not be carried out.
Often rendered as a circle with a line through it.
grab
Indicates that something can be grabbed (dragged to be moved).
Often rendered as the backside of an open hand.
grabbing
Indicates that something is being grabbed (dragged to be moved).
Often rendered as the backside of a hand with fingers closed mostly out of view.
resizing and scrolling cursors
e-resize
n-resize
ne-resize
nw-resize
s-resize
se-resize
sw-resize
w-resize
Indicates that some edge is to be moved. For example, the
se-resize
cursor is used when the movement starts from the
south-east corner of the box.
ew-resize
ns-resize
nesw-resize
nwse-resize
Indicates a bidirectional resize cursor.
col-resize
Indicates that the item/column can be resized horizontally.
Often rendered as arrows pointing left and right with a vertical bar separating them.
row-resize
Indicates that the item/row can be resized vertically.
Often rendered as arrows pointing up and down with a horizontal bar separating them.
all-scroll
Indicates that the something can be scrolled in any direction.
Often rendered as arrows pointing up, down, left, and right with a dot in the middle.
zooming cursors
zoom-in
zoom-out
Indicates that something can be zoomed (magnified) in or out, and
often rendered as a magnifying glass with a "+" or "-" in the center of the glass, for
zoom-in
and
zoom-out
respectively.
6.1.1.2.
Cursor of the canvas
The document
canvas
is the infinite surface over which the document is rendered
[CSS2]
Since no element corresponds to the canvas,
in order to allow styling of the cursor when not over any element,
the canvas cursor re-uses the root element’s cursor.
However, if no boxes are generated for the root element
(for example, if the root element has
display: none
),
then the canvas cursor is the platform-dependent default cursor.
Note:
An element might be invisible,
but still generate boxes. For example,
if the element has
visibility: hidden
but not
display: none
boxes are generated for it and its cursor is used for the canvas.
6.2.
Insertion caret
6.2.1.
Coloring the Insertion Caret: the
caret-color
property
Name:
caret-color
Value:
auto

Initial:
auto
Applies to:
all elements
Inherited:
yes
Percentages:
N/A
Computed value:
The computed value for
auto
is
auto
the computed value of
currentColor
is
currentColor
(See
currentcolor
);
see the
color
property for other

values.
Canonical order:
per grammar
Animation type:
color
by computed value
auto
User agents should use currentColor.
User agents may automatically adjust the color of caret
to ensure good visibility and contrast with the surrounding content,
possibly based on the currentColor, background, shadows, etc.

The insertion caret is colored with the specified color.
The caret is a visible indicator of the insertion point in an element where text (and potentially other content) is inserted by the user. This property controls the color of that visible indicator.
Note:
caret shape and blinking is outside the scope of this feature and thus unspecified.
Note:
UAs might have additional things that count as “carets”.
For example, some UAs can show a “navigation caret”,
which acts similarly to an insertion caret
but can be moved around in non-editable text,
and is functionally a caret.
On the other hand, the cursor image shown
when hovering over text when the
cursor
property is
auto
or when hovering over an element where the
cursor
property is
text
or
vertical-text
though it sometimes resembles a caret, is not a caret (it’s a cursor).
Example: a textarea with
caret-color
#00aacc
6.3.
Keyboard control
6.3.1.
Obsolete: the ime-mode property
"ime-mode" is a property somewhat implemented in some browsers, that is problematic and officially obsoleted by this specification.
User agents should not support the
ime-mode
property.
Authors must not use the ime-mode property.
Users may use the ime-mode property only for repair use-cases where they have to work around bad sites and legacy implementations, e.g. with a user style sheet rule like:
Example: user preference
input
type=password
ime-mode
auto !important
This example CSS may be placed into a user style sheet file to force password input fields to behave in a default manner.
This specification deliberately does not attempt to document the functionality of legacy ime-mode implementations nor what they specifically support because it does not make sense to pursue or recommend any such path.
Note: there are several
[HTML]
features which authors should use to provide information to user agents that allow them to provide a better input user experience:
The global
lang
attribute
The
inputmode
pattern
and
type
attributes of the input element
Appendix A: Acknowledgments
This appendix is
informative
This specification was edited and written for the most part
by Tantek Çelik from 1999 to the present,
first while representing Microsoft, then as an Invited Expert,
and most recently while representing Mozilla.
Thanks to
Florian Rivoal
, working on this specification on behalf of Bloomberg, for
his recent work documenting issues from www-style emails,
proposing resolutions & changes,
and in particular for researching & writing greatly
improved details for the
box-sizing
property.
Thanks to feedback and contributions from
Rossen Atanassov
Tab Atkins
L. David Baron
Bert Bos
Matthew Brealey
Rick Byers
Ada Chan
James Craig
Michael Cooper
Axel Dahmen
Michael Day
Micah Dubinko
Elika E.
Steve Falkenburg
Andrew Fedoniouk
Al Gilman
Ian Hickson
Bjoern Hoehrmann
Alan Hogan
David Hyatt
Richard Ishida
Sho Kuwamoto
Yves Lafon
Stuart Langridge
Susan Lesch
Peter Linss
Kang-Hao Lu
Masayuki Nakano
Mats Palmgren
Brad Pettit
Chris Rebert
François Remy
Andrey Rybka
Simon Sapin
Alexander Savenkov
Sebastian Schnitzenbaumer
Lea Verou
Etan Wexler
David Woolley
Frank Yan
Boris Zbarsky
and
Domel
Appendix B: Changes
This appendix is
informative
Changes from the
21 June 2018 Recommendation (REC)
Candidate Correction 1:
Referred to
scroll containers
instead of
overflow
values other than
visible
, so
clip
is included.
Candidate Correction 2:
Let computed value of
outline-width
be
snapped as a border width
Candidate Correction 3:
Updated and clarified computed value and animation type definitions.
Candidate Correction 4:
Removed the special case of
outline-width
having a computed value of 0 based on
outline-style: none
Update to modern terminology for consistency with other specifications, replacing relevant uses of terms 'intrinsic width/height/aspect ratio/size' to 'natural'.
Removed "Media" entries from property definitions. Its meaning has never been defined properly, and it does not add useful information.
Added
Value Definitions
section, for consistency with other CSS specifications.
Rearranged the description of the syntax of the
cursor
property for better readability.
Added Web Platform Tests coverage.
Split privacy and security considerations into separate sections.
Update references to other CSS modules to more contemporary ones.
Various other editorial improvements.
Changes from the
2 March 2017 Candidate Recommendation (CR)
Updated references to latest versions
Editorial Clarification about the resize property
Move (at risk) directional focus navigation properties from level 3 to level 4
Added informative link to HTML about special handling of
cursor
over image maps
Clarified (as a SHOULD) the implications of text-overflow on pointer events to capture implementor consensus (
corresponding test
).
Clarified that UAs may ignore the cursor property to reflect the UA’s UI state
Allowed, but stopped requiring support for SVG images without natural sizes for cursors (
corresponding test update
).
Aligned the spec with implementations, and make
cursor: auto
look like
text
over
selectable
text, and over editable elements (
corresponding tests
).
Appendix C: Privacy Considerations
The W3C TAG is developing a
Self-Review Questionnaire: Security and Privacy
for editors of specifications to informatively answer.
Per the
Questions to Consider
Does this specification deal with personally-identifiable information?
No.
Does this specification deal with high-value data?
No.
Does this specification introduce new state for an origin that persists across browsing sessions?
No.
Does this specification expose persistent, cross-origin state to the web?
No.
Does this specification expose any other data to an origin that it doesn’t currently have access to?
No.
Does this specification allow an origin access to a user’s location?
No.
Does this specification allow an origin access to sensors on a user’s device?
No.
Does this specification allow an origin access to aspects of a user’s local computing environment?
No.
Does this specification allow an origin access to other devices?
No.
Does this specification expose temporary identifiers to the web?
No.
Does this specification distinguish between behavior in first-party and third-party contexts?
No.
How should this specification work in the context of a user agent’s "incognito" mode?
No differently.
Does this specification persist data to a user’s local device?
No.
Appendix D: Security Considerations
This appendix is
informative
The W3C TAG is developing a
Self-Review Questionnaire: Security and Privacy
for editors of specifications to informatively answer.
Per the
Questions to Consider
Does this specification enable new script execution/loading mechanisms?
Yes to loading, but not to execution. The
cursor
property accepts

values which may include URLs to be loaded.
These may be SVG documents which may contain scripts,
but this specification requires that scripts must not be run.
Does this specification allow an origin some measure of control over a user agent’s native UI?
Yes. The
cursor
and
caret-color
properties enable the page to change the display of the cursor and text insertion caret of the user agent’s native UI.
In addition the
outline-style
property’s
auto
value (and thus
outline
shorthand) enable the page to potentially display a native focused element outline presentation around any element.
Does this specification allow downgrading default security characteristics?
No.
Appendix E: Default style sheet additions for HTML
This appendix is
informative
Potential additions to the base style sheet to express HTML form controls, and a few dynamic presentation attributes:
:enabled:focus
outline
px
inset
button
input
type=button
],
input
type=reset
],
input
type=submit
],
input
type=checkbox
],
input
type=radio
],
textarea
input
input
type=text
],
input
type=password
],
input
type=image
display
inline-block
input
type=button
],
input
type=reset
],
input
type=submit
],
input
type=checkbox
],
input
type=radio
],
input
input
type=text
],
input
type=password
],
input
type=image
white-space
nowrap
button
/* white space handling of BUTTON tags in particular */
white-space:normal
input
type=reset
:lang
en
/* default content of HTML input type=reset button, per language */
content:
"Reset"
input
type=submit
:lang
en
/* default content of HTML input type=submit button, per language */
content:
"Submit"
/* UAs should use language-specific Reset/Submit rules for others. */
input
type=button
],
input
type=reset
][
value
],
input
type=submit
][
value
/* text content/labels of HTML "input" buttons */
content:
attr
value
);
textarea
/* white space handling of TEXTAREA tags in particular */
white-space:pre-wrap
resize
both
input
type=hidden
/* appearance of the HTML hidden text field in particular */
display: none !important
input
type=image
content
attr
src
url
);
border
none
select
size
/* HTML4/XHTML1 w/ size more than 1 - appearance of list */
display: inline-block
height
attr
size
em
);
select
select
size=
/* HTML4/XHTML1 without size, or size=1 - popup-menu */
display: inline-block
height
em
overflow
hidden
select
size
:active
/* active HTML w/ size more than 1 - appearance of active list */
display: inline-block
optgroup
option
display
block
white-space
nowrap
optgroup
label
],
option
label
content
attr
label
);
option
selected
::before
display
inline
content
check
/* Though FRAME resizing is not directly addressed by this specification,
the following rules may provide an approximation of reasonable behavior. */
/*
frame {
resize:both;
frame[noresize] {
resize:none
*/
Conformance
Document conventions
Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes.
[RFC2119]
Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with
class="example"
like this:
This is an example of an informative example.
Informative notes begin with the word “Note” and are set apart from the
normative text with
class="note"
, like this:
Note, this is an informative note.
Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with

, like
this:
UAs MUST provide an accessible alternative.
Conformance classes
Conformance to this specification
is defined for three conformance classes:
style sheet
CSS
style sheet
renderer
UA
that interprets the semantics of a style sheet and renders
documents that use them.
authoring tool
UA
that writes a style sheet.
A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
Partial implementations
So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers
must
treat as invalid (and
ignore
as appropriate
) any at-rules, properties, property values, keywords,
and other syntactic constructs for which they have no usable level of
support. In particular, user agents
must not
selectively
ignore unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid
(as unsupported values must be), CSS requires that the entire declaration
be ignored.
Implementations of Unstable and Proprietary Features
To avoid clashes with future stable CSS features,
the CSSWG recommends
following best practices
for the implementation of
unstable
features and
proprietary extensions
to CSS.
Non-experimental implementations
Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they
can demonstrate to be correctly implemented according to spec.
To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group.
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at
Questions should be directed to the
public-css-testsuite@w3.org
mailing list.
Index
Terms defined by this specification
alias
, in § 6.1.1.1
all-scroll
, in § 6.1.1.1
auto
value for caret-color
, in § 6.2.1
value for cursor
, in § 6.1.1.1
border-box
, in § 3.1
box-sizing
, in § 3.1
caret-color
, in § 6.2.1
cell
, in § 6.1.1.1
clip
, in § 5.2
col-resize
, in § 6.1.1.1
content-box
, in § 3.1
context-menu
, in § 6.1.1.1
copy
, in § 6.1.1.1
crosshair
, in § 6.1.1.1
cursor
, in § 6.1.1

, in § 6.1.1

(type)
, in § 6.1.1.1
value for cursor
, in § 6.1.1
default
, in § 6.1.1.1
ellipsis
, in § 5.2
e-resize
, in § 6.1.1.1
ew-resize
, in § 6.1.1.1
grab
, in § 6.1.1.1
grabbing
, in § 6.1.1.1
help
, in § 6.1.1.1
invert
, in § 4.4
max inner height
, in § 3.1
max inner width
, in § 3.1
min inner height
, in § 3.1
min inner width
, in § 3.1
move
, in § 6.1.1.1
ne-resize
, in § 6.1.1.1
nesw-resize
, in § 6.1.1.1
no-drop
, in § 6.1.1.1
none
, in § 6.1.1.1
not-allowed
, in § 6.1.1.1
n-resize
, in § 6.1.1.1
ns-resize
, in § 6.1.1.1
nw-resize
, in § 6.1.1.1
nwse-resize
, in § 6.1.1.1
outline
, in § 4.1
outline-color
, in § 4.4
outline-offset
, in § 4.5
outline-style
, in § 4.3
outline-width
, in § 4.2
pointer
, in § 6.1.1.1
progress
, in § 6.1.1.1
resize
, in § 5.1
row-resize
, in § 6.1.1.1
se-resize
, in § 6.1.1.1
s-resize
, in § 6.1.1.1
sw-resize
, in § 6.1.1.1
text
, in § 6.1.1.1
text-overflow
, in § 5.2
vertical-text
, in § 6.1.1.1
wait
, in § 6.1.1.1
w-resize
, in § 6.1.1.1
zoom-in
, in § 6.1.1.1
zoom-out
, in § 6.1.1.1
Terms defined by reference
[CSS-BACKGROUNDS-3]
defines the following terms:

background-image
border-bottom-width
border-left-width
border-radius
border-right-width
border-style
border-top-width
border-width
none
[CSS-CASCADE-5]
defines the following terms:
computed value
[CSS-COLOR-4]
defines the following terms:
color
currentcolor
[CSS-COLOR-5]
defines the following terms:

[CSS-GAPS-1]
defines the following terms:
column-rule-width
[CSS-IMAGES-3]
defines the following terms:

concrete object size
default object size
default sizing algorithm
natural aspect ratio
natural size
[CSS-OVERFLOW-3]
defines the following terms:
clip
overflow
scroll container
visible
[CSS-PSEUDO-4]
defines the following terms:
CSSPseudoElement
[CSS-VALUES-4]
defines the following terms:



CSS-wide keywords
snap as a border width
{A}
||
[CSS-WRITING-MODES-3]
defines the following terms:
direction
left
[CSS-WRITING-MODES-4]
defines the following terms:
end
[CSS2]
defines the following terms:
auto
border edge
bottom
content height
content width
display
height
left
margin-left
margin-top
max-height
max-width
min-height
min-width
padding-bottom
padding-left
padding-right
padding-top
right
top
visibility
width
[HTML]
defines the following terms:
canvas
iframe
img
object
picture
video
[SVG2]
defines the following terms:
svg
[WEB-ANIMATIONS-1]
defines the following terms:
animation type
References
Normative References
[CSS-BACKGROUNDS-3]
Elika Etemad; Brad Kemper.
CSS Backgrounds and Borders Module Level 3
. 11 March 2024. CRD. URL:
[CSS-CASCADE-5]
Elika Etemad; Miriam Suzanne; Tab Atkins Jr..
CSS Cascading and Inheritance Level 5
. 13 January 2022. CR. URL:
[CSS-COLOR-4]
Tab Atkins Jr.; Chris Lilley; Lea Verou.
CSS Color Module Level 4
. 31 March 2026. CRD. URL:
[CSS-COLOR-5]
Chris Lilley; Una Kravets; Lea Verou.
CSS Color Module Level 5
. 25 March 2026. WD. URL:
[CSS-IMAGES-3]
Tab Atkins Jr.; Elika Etemad; Lea Verou.
CSS Images Module Level 3
. 18 December 2023. CRD. URL:
[CSS-OVERFLOW-3]
Elika Etemad; Florian Rivoal.
CSS Overflow Module Level 3
. 7 October 2025. WD. URL:
[CSS-VALUES-3]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 3
. 22 March 2024. CRD. URL:
[CSS-VALUES-4]
Tab Atkins Jr.; Elika Etemad.
CSS Values and Units Module Level 4
. 12 March 2024. WD. URL:
[CSS-WRITING-MODES-4]
Elika Etemad; Koji Ishii.
CSS Writing Modes Level 4
. 30 July 2019. CR. URL:
[CSS2]
Bert Bos; et al.
Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification
. 7 June 2011. REC. URL:
[HTML]
Anne van Kesteren; et al.
HTML Standard
. Living Standard. URL:
[PNG]
Chris Lilley; et al.
Portable Network Graphics (PNG) Specification (Third Edition)
. 24 June 2025. REC. URL:
[RFC2119]
S. Bradner.
Key words for use in RFCs to Indicate Requirement Levels
. March 1997. Best Current Practice. URL:
[SVG11]
Erik Dahlström; et al.
Scalable Vector Graphics (SVG) 1.1 (Second Edition)
. 16 August 2011. REC. URL:
[SVG2]
Amelia Bellamy-Royds; et al.
Scalable Vector Graphics (SVG) 2
. 4 October 2018. CR. URL:
[UAX29]
Josh Hadley.
Unicode Text Segmentation
. 17 August 2025. Unicode Standard Annex #29. URL:
[WEB-ANIMATIONS-1]
Brian Birtles; et al.
Web Animations
. 5 June 2023. WD. URL:
Informative References
[CSS-CASCADE-4]
Elika Etemad; Tab Atkins Jr..
CSS Cascading and Inheritance Level 4
. 13 January 2022. CR. URL:
[CSS-GAPS-1]
Kevin Babbitt.
CSS Gap Decorations Module Level 1
. 27 February 2026. WD. URL:
[CSS-PSEUDO-4]
Elika Etemad; Alan Stearns.
CSS Pseudo-Elements Module Level 4
. 27 June 2025. WD. URL:
[CSS-WRITING-MODES-3]
Elika Etemad; Koji Ishii.
CSS Writing Modes Level 3
. 10 December 2019. REC. URL:
[CSS1]
Håkon Wium Lie; Bert Bos.
Cascading Style Sheets, level 1
. 13 September 2018. REC. URL:
[CSS4-IMAGES]
Elika Etemad; Tab Atkins Jr.; Lea Verou.
CSS Images Module Level 4
. 30 September 2025. WD. URL:
Property Index
Name
Value
Initial
Applies to
Inh.
%ages
Anim­ation type
Canonical order
Com­puted value
box-sizing
content-box | border-box
content-box
all elements that accept width or height
no
N/A
discrete
per grammar
specified value
caret-color
auto |
auto
all elements
yes
N/A
colorby computed value
per grammar
The computed value for auto is auto;
the computed value of currentColor is currentColor (See currentcolor);
see the color property for other values.
cursor
[,]*
auto
all elements
yes
N/A
discrete
per grammar
as specified, except with any relative URLs converted to absolute
outline
[ <'outline-color'> || <'outline-style'> || <'outline-width'> ]
see individual properties
all elements
no
N/A
see individual properties
per grammar
see individual properties
outline-color
| invert
invert
all elements
no
N/A
colorby computed value
per grammar
The computed value for invert is invert;
the computed value of currentColor is currentColor (See currentcolor);
see the color property for other values.
outline-offset

all elements
no
N/A
lengthby computed value
per grammar
value in absolute units (px or physical).absolute length
outline-style
auto |
none
all elements
no
N/A
discrete
per grammar
as specified
outline-width

medium
all elements
no
N/A
lengthby computed value
per grammar
absolute length, snapped as a border width; 0 if the outline style is none.
resize
none | both | horizontal | vertical
none
elements with overflow other than visible,that are scroll containers
and optionally replaced elements such as images, videos, and iframes
no
N/A
discrete
per grammar
as specified keyword
text-overflow
clip | ellipsis
clip
block containers
no
N/A
discrete
per grammar
as specified keyword

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