Open Bug 1684605 Opened 3 years ago Updated 2 months ago

Implement @property at-rule


(Core :: CSS Parsing and Computation, enhancement)





(Reporter: sebo, Unassigned)


(Depends on 1 open bug, Blocks 2 open bugs, )


(5 keywords)


(1 obsolete file)

This bug is meant to track the implementation of the @property at-rule defined in the CSS Houdini Properties and Values specification which allows to define custom properties in CSS.


This is a useful feature. See the Stack Overflow post: animating gradients in CSS for a use case.

Is there any estimate for when it will be implemented?

The related bug in Webkit (Safari):

No estimate right now, though patches welcome? has a parser for the typed-om syntax that could be used to prototype this.

@property was recently enabled in WebKit:

See Also: → 1821552

Removing dev-doc-needed keyword since exists at this point. (Feel free to add back with details on what's needed if I'm missing something, though.)

Blocks: interop-2023
Keywords: dev-doc-needed
No longer blocks: interop-2023

Well, unless the MDN team works differently nowadays, dev-doc-needed indicates that the related browser compatibility data entry needs to be updated once this feature landed.
I also assume that this will initially be implemented behind a pref. In that case it should also be documented at So I added the keyword back.
Once there's a bug to ship @property (maybe together with the DOM API), dev-doc-needed should also be added there in order to update the browser compat data and remove it from the experimental features page again once that bug is closed.


Keywords: dev-doc-needed
Depends on: 1833538
Depends on: 1833539
Depends on: 1833540
No longer depends on: 1833538, 1833539
Blocks: 1841023
Attachment #9345316 - Attachment is obsolete: true
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