This is the Mozilla wiki home page for Cascading Style Sheets (CSS).

CSS

Platform priorities

The following CSS specs/proposal are a priority for the Platform.

Actively Implementing

Flexbox

Mozilla has a pretty solid complete Flexbox (W3C CR, just waiting on feature-interaction tests to go PR) implementation. We are working on some fixes to make it even better, e.g.

Grid

CSS Grid (CR, another CR expected Q1 2017) metabug
- lots of work

Grid Level 2

CSS Grid level 2 specifically for subgrid
doing some exploratory implementing, design may (hopefully likely) change accordingly

Shapes

CSS Shapes (CR, another CR expected Q1 2017) metabug
- shape-outside

Box Alignment

CSS Box Alignment (WD), metabug
- all properties for blocks (1040695, 1105571)
- and some details for flexbox (see 1105570 Depends on)
- spec CR depends on resolving open css-align-3 issues

Multi-column

CSS Multi-column Layout (CR, but multicol editor's draft has changes), metabug
- unprefixing, column-span, a11y bug hack removal, column-break
- Alias page-break-* to break-*: https://bugzilla.mozilla.org/show_bug.cgi?id=775618

(Jen has a demo of bugs / test page at http://labs.jensimmons.com/examples/multicolumn-3-bug-demo.html)

Containment

CSS Containment Module Level 3 (ED) 'contain' property, size/layout, style, paint
- Main bug: bug 1150081

3D Transforms

3D Transform interop / spec changes, "3d transform" bugs

intrinsic size keywords: fix bug 567039 and bug 1055887 and maybe others and unprefix (meta: 1312587)

Text Decoration

CSS Text Decoration Module Level 3 (CR) (metabug)

focusing on text-decoration-skip https://bugzilla.mozilla.org/show_bug.cgi?id=812990
text-emphasis (remaining bugs)
text-underline-position
What else left for this module? (JS)

Under the hood and related

Intersection observer (intent to ship coming)
Resize observer (intent to implement coming)
Stylo
Web Animations API (metabug)
PDF viewer support (PDFium bug#?)
- Project Mortar: https://wiki.mozilla.org/Mortar_Project
- Possible meta bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1049218
- Platform support: https://bugzilla.mozilla.org/show_bug.cgi?id=1302489

Evaluating

Font Rendering Controls

CSS Font Rendering Controls Module Level 1 (ED)

focusing on font-display descriptor https://bugzilla.mozilla.org/show_bug.cgi?id=1317445 (implemented behind a flag, other browsers too)

Font Loading

CSS Font Loading Module Level 3 https://developer.mozilla.org/en-US/docs/Web/API/CSS_Font_Loading_API shipped in 41

CSS Font Loading Improvements, Multiple bugs e.g., https://bugzilla.mozilla.org/show_bug.cgi?id=1157064

Other

font inflation removed
CSS Transform properties (shorthands)

Related HTML5

HTML5 layout and presentation related work:

srcset intrinsic size
dialog element (fullscreen interactions, and since showModalDialog being deprecated/removed) #840640
...

Recent CRs

At the TPAC 2016 CSS WG f2f, the WG resolved to work on taking the following WDs to CR by end of 2016.

Recent CRs before the f2f:

Cascading and Inheritance

CSS Cascading and Inheritance Level 3 (CR), metabug
- New features since CSS2.x
  - scoped styles, animations, and transitions in the cascade.

These have made it into CR since that f2f:

Scroll Snap (CR), metabug
- Fix related bugs
Grid (see above)

Upcoming CRs

These CRs are expected by 2017 Q1:

For all potential CRs:

Which browsers have openly announced implementations or intent to implement? (links?)

Box Alignment (see above)

Text Level 3

Text (need list of changes since CSS 2.1), metabug

Expected 2017 CRs

Several WDs and existing CRs were expected to be (re)published as CRs in 2017 Q1, at the 2017-01-12 CSSWG f2f (see IRC log / minutes for that day).

Selectors 4

Selectors 4 (need list of changes since 3), metabug

No explicit dependency on Stylo, just lower priority
Selectors4 remaining features
- CSS ::selection fixes + unprefixing
- ... remaining new features? (JS)

Shipping Soon

As the above priorities get implemented, moving down here to note we're waiting for them to ship.

51:

CSS :placeholder-shown (shipping in 51)

52:

CSS :focus-within (shipping in 52)

Post Stylo Integration

CSS Color Level 4

CSS Color Module Level 4 (ED)

Color improvements (wide gamut, color correction, note CSS color correction preffed off)
The "making rgb/hsl equivalent to rgba/hsla" piece has already landed, in bug 1295456

Media Queries 4

Media Queries 4 (note: new features in 4), metabug
- full support of numerical comparators (<, <=, =>, >)
- expansion of negation syntax (and, or, not)
- interaction features #1035774

Values and Units 3

CSS Values and Units Module Level 3 (CR)

[ ] attr function (at risk) — very useful in combination with CSS Shapes, in the context of a CMS

Image Values and Replaced Content

CSS Image Values and Replaced Content Module Level 3 (CR)

image() function
[ ] xywh fragment syntax

Style sheet APIs for Add-ons

style sheet APIs in add-ons SDK / loading async APIs (to be handled by stylo)

Filter Effects Level 2

Filter Effects Module Level 2: backdrop-filter
- backdrop-filter bug (caniuse: only Safari supports)
- also on Trello Future Backlog

Motion Path Module

https://www.w3.org/TR/motion-1/ (currently Working Draft)

Device Adaptation

CSS Device Adaptation Module Level 1 (ED)

Houdini

CSS Houdini - see inside for Houdini implementation thoughts/plan

properties

Please add subpages for each (unprefixed) CSS property in alphabetical order.

...
overflow
...
text-overflow
...

in development

CSS properties which have not yet made it to a Candidate Recommendation (or later), or are only implemented in the wild in prefixed form.

new pseudo-classes

...
:autofill
...

new properties

...
text-size-adjust (-moz-, -ms-, -webkit-)
...

CSS

CSS