← back to v143 · at-rule-css-feature-detection

conformance · v143

v143 · at-rule-css-feature-detection — conformance probe

7 assertions drawn from the spec. Each is a single contract the spec text makes. Pass/fail reflects what this browser executed; blocked means the contract was not run because it needs user mediation, hardware, or another unavailable precondition. Open the page in Chrome stable / canary / Firefox / Safari to compare.

browser: spec: https://drafts.csswg.org/css-conditional-5/#support-definition-at-rules chromestatus: #5110744177836032 generated 2026-06-05T12:11:00Z by manual-codex-devtools-mcp
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pass
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fail
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blocked
7
total
id contract kind verdict detail
supports-at-rule-container @supports at-rule(@container) reports true because @container is supported. spec ↗ script
supports-at-rule-media @supports at-rule(@media) reports true. spec ↗ script
supports-at-rule-unknown at-rule() reports false for an unknown at-keyword. spec ↗ script
supports-at-rule-charset-false Per spec, @charset is not a real at-rule, so at-rule(@charset) returns false. spec ↗ script
supports-at-rule-supports at-rule(@supports) reports true since @supports itself is supported. spec ↗ script
supports-at-rule-requires-at-keyword at-rule() requires an at-keyword argument (the leading @ is part of the token). spec ↗ script
supports-at-rule-rejects-full-rule-snippet at-rule() takes only an at-keyword token, so descriptor-like full rule snippets are not valid arguments. spec ↗ script