Creating this as the implementation bug for Bug 1751188. This support condition will be implemented behind the `layout.css.supports.at-rule.enabled` pref, enabled in Nightly by default. --- **Release Note Request (optional, but appreciated)** [Why is this notable]: New CSS feature, parity with Chrome [Affects Firefox for Android]: Yes [Suggested wording]: Firefox Nightly now supports the [`at-rule()`](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules/@supports#at-rule) function for `@supports`. This allows authors to detect for browser support of specific at-rules, such as `@supports at-rule(@scope)`. [Links (documentation, blog post, etc)]: - https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules/@supports#at-rule\ - https://www.bram.us/2026/03/15/at-rule/
Bug 2060754 Comment 0 Edit History
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Creating this as the implementation bug for Bug 1751188. This support condition will be implemented behind the `layout.css.supports.at-rule.enabled` pref, enabled in Nightly by default. --- **Release Note Request (optional, but appreciated)** [Why is this notable]: New CSS feature, parity with Chrome [Affects Firefox for Android]: Yes [Suggested wording]: Firefox Nightly now supports the [`at-rule()`](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules/@supports#at-rule) function for `@supports`. This allows authors to detect for browser support of specific at-rules, such as `@supports at-rule(@scope)`. [Links (documentation, blog post, etc)]: - https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules/@supports#at-rule - https://www.bram.us/2026/03/15/at-rule/