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…S Detection Fixes #64 The media/onload deferral pattern (media="print" onload="this.media='all'") was incorrectly flagged as render-blocking. By the time the snippet runs, the onload handler has already mutated the media attribute to "all", making the DOM-based check unreliable. Now uses PerformanceResourceTiming.renderBlockingStatus (Chrome 107+) as the primary signal — it reflects actual render-blocking during page load. The DOM heuristic is kept as a fallback with a comment noting its limitation.
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Closes #64
Summary
mediaattribute check withPerformanceResourceTiming.renderBlockingStatusas the primary signalmedia="print" onload="this.media='all'"deferral pattern — stylesheets loaded this way are now reported as non-blockingrenderBlockingStatussupport (pre-Chrome 107), with a comment noting the known limitationRoot Cause
The snippet read
link.getAttribute("media")at runtime. By that point, theonloadhandler from the deferral pattern has already changed the attribute from"print"to"all", so the check incorrectly flagged those stylesheets as render-blocking.Test plan
media="print" onloadshould appear in the Non-Blocking section, not Render-BlockingrenderBlockingStatussupport — fallback DOM check activatesBefore
After