[CSSWG][css-contain] Update CR of CSS Conain L1

(This mail should have been sent much earlier. Apologies for the belated announcement).

The CSS WG has published a Candidate Recommendation and invites implementations of the CSS Containment Module Level 1:


This CSS module describes the contain property, which indicates that the element’s subtree is independent of the rest of the page. This enables heavy optimizations by user agents when used well.

This is a minor update, driven by implementation experience and testing, focused on bug fixing and clarifications. Barring anything unexpected, the CSS-WG expects little to no change after this. People who intend to review this specification but have not yet had the chance to do so are strongly encouraged to look at it as soon as possible, as implementations are progressing, and growing usage in the wild will increasingly limit possible changes.

Significant changes are listed at:


A comprehensive test suite for the full specification was developed, see:


Disposition of comments:

Please review the draft, and send any comments to this mailing list,
<www-style@w3.org>, prefixed with [css-contain] (as I did on this
message) or (preferably) file them in the GitHub repository at

For the CSS WG,

Received on Monday, 4 February 2019 05:14:55 UTC