CSS Scrollbars standardizes the ability to color scrollbars introduced in 2000 by Windows IE 5.5.
This is useful when building web applications which use color schemes very different from
the appearance of default platform scrollbars.
CSS is a language for describing the rendering of structured documents
(such as HTML and XML)
on screen, on paper, in speech, 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.
GitHub Issues are preferred for discussion of this specification.
When filing an issue, please put the text “css-scrollbars” in the title,
preferably like this:
“[css-scrollbars] …summary of comment…”.
All issues and comments are archived,
and there is also a historical archive.
This module adds color properties for styling the scrollbar (if any) of an element per documented use-cases,
and as has been increasingly adopted
on the web since Windows IE 5.5 introduced it in 2000.
[Note: Add citations of examples from Bugzilla 77790 and webcompat].
In addition to the property-specific values listed in their definitions,
all properties defined in this specification
also accept the CSS-wide keywords keywords as their property value.
For readability they have not been repeated explicitly.
These properties allow the author to set colors for various aspects of an element’s scrollbars.
Note: Per Issue 1960,
the list of scrollbar-*-color properties is likely to be reduced to 2-3 (ideally 2),
with current candidates being scrollbar-base-color, scrollbar-face-color, scrollbar-track-color,
per research so far,
and preferably only two of those. Additional input, data, suggestions welcome at those links!
UAs must apply the scrollbar-* values set on the root element to the viewport.
Note: Unlike overflow (and overflow-*) properties,
scrollbar-* values set on the HTML body element are not propagated to viewport.
default platform rendering for that portion of the scrollbar, in the absence of any other
related scrollbar color properties. See details below for which scrollbar color are related to which.
apply the color to that portion of the scrollbar, and potentially other portions of the scrollbar.
If scrollbar-track-color computes to auto, and scrollbar-face-color and scrollbar-highlight-color are not auto,
they are combined (e.g. dithered) to color the scrollbar track.
If just one of scrollbar-face-color and scrollbar-highlight-color is not auto, it is used to color the scrollbar track.
If scrollbar-face-color computes to auto and scrollbar-base-color is not auto,
then use its value for scrollbar-face-color.
If scrollbar-3dlight-color computes to auto and scrollbar-base-color is not auto,
then use its value for scrollbar-3dlight-color.
If an element has both horizontal and vertical scrollbars, and the scrollbar-face-color is not auto,
use it for the area in the corner between the two scrollbars.
If the color of any part of the scrollbar is specified,
implementations may render a simpler scrollbar than the default platform UI rendering, and color it accordingly.
(Note: add example of an overflow element with colorized scrollbars to match page styling,
PNG of the same in a browser that supports it currently)
Implementations may ignore any scrollbar color properties for scrollbar parts that do not exist
on the underlying platform.
Note: when a user interacts with a scrollbar (e.g. arrow buttons or scroll thumb if any),
implementations may alter which scrollbar colors apply to which scrollbar parts (e.g. replace 3dlight and darkshadow colors with their shadow color, and highlight and shadow colors with their face color.
Note: IE uses named System Colors as defaults for each of the scrollbar color properties.
See related Issue 1956.
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",
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 <strong class="advisement">, like
this: UAs MUST provide an accessible alternative.
Conformance to this specification
is defined for three conformance classes:
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.
Requirements for Responsible Implementation of CSS
The following sections define several conformance requirements
for implementing CSS responsibly,
in a way that promotes interoperability in the present and future.
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 property 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
Once a specification reaches the Candidate Recommendation stage,
implementers should release an unprefixed implementation
of any CR-level feature they can demonstrate
to be correctly implemented according to spec,
and should avoid exposing a prefixed variant of that feature.
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