loading.render-blocking-script
Scripts in <head> load without async, defer or type="module", so the browser stops building the page until each one has downloaded and run.
What to change
Add defer to scripts the page needs once it is parsed, or async to independent ones such as analytics; type="module" scripts are deferred already. A script that must run before anything renders (a consent manager, an A/B test) can stay, but keep it small.
The documentation on developer.chrome.comA finding of this rule on a page carries the exact edits for that page: the markup it quotes, and what to write instead.
When it runs
Runs on every SEO audit: of a page, a crawl, a build directory or HTML. Info is a best practice: worth doing, rarely urgent, and --no-info leaves it out. Each finding takes 1 point off the page's score.
The severity here is the rule's usual one: a finding can be raised or lowered when the page gives a reason.
Run it, or skip it
Check a page for this rule alone, after a fix for instance:
npx @rivi-software/agentic-seo-check audit https://example.com --rule loading.render-blocking-scriptOr from an assistant, with the MCP tool seo_audit_page:
{
"url": "https://example.com",
"rules": [
"loading.render-blocking-script"
]
}To leave it out of an audit, pass --disable loading.render-blocking-script on the command, or disableRules: ["loading.render-blocking-script"] to a tool.
More in Performance
All 17 rules- Warning
loading.no-compressionThe HTML is sent uncompressed although the request accepted gzip, so every visitor and crawler downloads several times more bytes than needed. - Warning
perf.field-lcp-poorOn phones, real visits wait more than 4,000 ms for the largest element of the first screen at the 75th percentile: Largest Contentful Paint (LCP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it poor. - Warning
perf.field-inp-poorOn phones, real visits wait more than 500 ms for the page to answer a tap or a key at the 75th percentile: Interaction to Next Paint (INP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it poor. - Warning
perf.field-cls-poorOn phones, the layout of real visits shifts by more than 0.25 at the 75th percentile: Cumulative Layout Shift (CLS) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it poor. - Info
perf.field-lcp-needs-improvementOn phones, real visits wait more than 2,500 ms for the largest element of the first screen at the 75th percentile: Largest Contentful Paint (LCP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement. - Info
perf.field-inp-needs-improvementOn phones, real visits wait more than 200 ms for the page to answer a tap or a key at the 75th percentile: Interaction to Next Paint (INP) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement. - Info
perf.field-cls-needs-improvementOn phones, the layout of real visits shifts by more than 0.10 at the 75th percentile: Cumulative Layout Shift (CLS) in the Chrome UX Report's last 28 days, for the page's URL or, when it has too few visits, its origin. Google rates it as needing improvement. - Warning
perf.lcp-slowLargest Contentful Paint above 2.5 s (poor above 4 s). Lab measurement from Lighthouse.