Audit rules

Render Blocking Scripts

External classic scripts in <head> without defer or async block rendering. Module scripts, scripts with another type (JSON-LD, templates), nomodule scripts and scripts in <body> are not counted. In a QuikSEO audit, a failure has info severity and counts against the score. The exact condition, its exceptions and its sources follow below.

01 — Definition

How This Rule Is Checked

The rule is a pure function of the fetched page: no extra requests, no account settings. The same input always gives the same result.

Rule Severity and Score

Rule id: performance.render_blocking_scripts
Group: Performance
Severity of a failure: Info
Counts in the score: Yes, whenever it applies to the page
Required for a score: No
Replaces the check: non_deferred_scripts

Condition and Exceptions

Condition: External classic scripts in <head> without defer, async or type=module → fail (info) with count
Exceptions: —

Sources

Sources: Eliminate render-blocking resources | Lighthouse | Chrome for Developers (Chrome for Developers, Q07)
HTML Standard (WHATWG), 4.12.1 The script element: async and defer attributes (WHATWG, Q53)

02 — Performance

Other Rules in This Group

The other checks of the same group, each with its own condition and sources.

DOM Sizeperformance.dom_size
HTTP Requestsperformance.http_requests
HTML Page Sizeperformance.page_size
Render Blocking Stylesheetsperformance.render_blocking_stylesheets
Response Timeperformance.response_time
Time to First Byteperformance.ttfb