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fix(performance): the render-blocking Lighthouse audit is now an insight #224

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fix(performance): the render-blocking Lighthouse audit is now an insight #224

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8 changes: 4 additions & 4 deletions src/content/spec/performance/critical-css.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ status: recommended
order: 80
appliesTo: [all]
relatedSlugs: [core-web-vitals, font-loading, preload-prefetch-preconnect]
updated: "2026-05-29T09:13:20.000Z"
updated: "2026-09-20T00:00:00.000Z"
sources:
- title: "web.dev — Extract critical CSS"
url: "https://web.dev/articles/extract-critical-css"
Expand All @@ -18,8 +18,8 @@ sources:
- title: "MDN — Render-blocking resources"
url: "https://developer.mozilla.org/en-US/docs/Glossary/Render_blocking"
publisher: "MDN"
- title: "Chrome for Developers — Eliminate render-blocking resources"
url: "https://developer.chrome.com/docs/lighthouse/performance/render-blocking-resources"
- title: "Chrome for Developers — Render-blocking requests"
url: "https://developer.chrome.com/docs/performance/insights/render-blocking"
publisher: "Google"
---

Expand Down Expand Up @@ -75,5 +75,5 @@ Use `async` only for truly independent third-party scripts.
## Verification

- DevTools → Performance → record a load. The "Render-Blocking" badge marks every blocking request.
- Lighthouse "Eliminate render-blocking resources" lists them with estimated savings.
- Lighthouse's "Render-blocking requests" insight lists them with estimated savings. (Before Lighthouse 13 this was the "Eliminate render-blocking resources" audit.)
- View source: every non-critical `<link rel="stylesheet">` should be deferred; every `<script>` in `<head>` should have `defer` or `async`.
8 changes: 4 additions & 4 deletions src/content/spec/performance/script-loading.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,16 +7,16 @@ status: recommended
order: 85
appliesTo: [all]
relatedSlugs: [critical-css, core-web-vitals, preload-prefetch-preconnect, resource-hints, lazy-loading]
updated: "2026-05-29T09:55:11.000Z"
updated: "2026-09-20T00:00:00.000Z"
sources:
- title: "HTML Living Standard — The script element"
url: "https://html.spec.whatwg.org/multipage/scripting.html#the-script-element"
publisher: "WHATWG"
- title: "MDN — <script>"
url: "https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/script"
publisher: "MDN"
- title: "Chrome for Developers — Eliminate render-blocking resources"
url: "https://developer.chrome.com/docs/lighthouse/performance/render-blocking-resources"
- title: "Chrome for Developers — Render-blocking requests"
url: "https://developer.chrome.com/docs/performance/insights/render-blocking"
publisher: "Google"
- title: "web.dev — JavaScript module scripts"
url: "https://web.dev/articles/modulepreload"
Expand Down Expand Up @@ -125,6 +125,6 @@ See [resource hints](/spec/performance/resource-hints/) for the decision table.

- View source on every page — every `<script src>` should have `defer`, `async`, or `type="module"` unless it is a tiny inline script with a documented reason.
- Chrome DevTools → Network → JS — column "Initiator" should show the script started loading during the initial HTML parse, not after.
- Lighthouse "Eliminate render-blocking resources" reports zero offending scripts.
- Lighthouse's "Render-blocking requests" insight reports zero offending scripts. (Before Lighthouse 13 this was the "Eliminate render-blocking resources" audit.)
- WebPageTest filmstrip — the first paint should not be delayed by JavaScript download/execution.
- For CSP compatibility, run [CSP Evaluator](https://csp-evaluator.withgoogle.com/) on production headers and confirm every `<script>` is allowed.
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