Async scripts in use

Questions about this rule

Does PERF_ASYNC_SCRIPTS affect my score?

No. It is a detection rule: it runs, appears in your report and never penalises you. "Async scripts in use" is information about the page rather than a defect - most pages are not expected to satisfy it.

What does SPECIFICATION confidence mean?

A standard says so: HTML, WCAG, an RFC or Google's own documentation. Confidence is a declared tier rather than a per-rule number, so every rule backed by the same class of evidence carries the same weight - which is what makes the score reproducible instead of hand-tuned.

How do I check PERF_ASYNC_SCRIPTS on my own site?

Paste your URL into the box above and it runs only this rule, usually in a couple of seconds. It is also included in the Performance checker and in a full scan.