Deferred Scripts
Checks that non-critical scripts use async or defer attributes.
What this check measures
We list all <script src> without async or defer. Each is render-blocking — browser stops parsing HTML until the script downloads and executes.
Why it matters
One render-blocking script in the head can add 1-2 seconds to first paint on slow connections. Async/defer cuts that to near-zero. Trivial fix for huge perf gain.
How our audit detects it
Parse <script src> tags. Flag those missing async and defer.
Typical findings
- error_outlineThird-party chat widget in head without async.
- error_outlinejQuery + plugins loaded synchronously — worst case.
How to fix
Add async to analytics and independent scripts. Use defer for scripts that depend on DOM but not on each other. Only synchronous scripts that block first paint should stay.
Frequently asked questions
async vs defer?expand_more
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PerformanceINP (Interaction to Next Paint)
Checks Interaction to Next Paint — responsiveness to clicks/taps. Target under 200ms.
PerformanceFCP (First Contentful Paint)
Checks First Contentful Paint — when the first text or image appears. Target under 1.8s.