Glossary · HTTP, edge and rendering
render-blocking resource
A stylesheet or synchronous script the browser must fetch and process before it can paint anything below it. Each one adds a network round trip to the first paint; deferring scripts and inlining or preloading critical CSS are the fixes.
What render-blocking resource means
A stylesheet or synchronous script the browser must fetch and process before it can paint anything below it. Each one adds a network round trip to the first paint; deferring scripts and inlining or preloading critical CSS are the fixes. The count is measured from the delivered HTML, not from a rendered timeline.
What render-blocking resource can and cannot support
| It can support | It cannot support |
|---|---|
| A stylesheet or synchronous script the browser must fetch and process before it can paint anything below it. Each one adds a network round trip to the first paint; deferring scripts and inlining or preloading critical CSS are the fixes. | The count is measured from the delivered HTML, not from a rendered timeline. |
Related terms in HTTP, edge and rendering
The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
Origin server · Reverse proxy · CDN · Edge node · WAF · Bot score · TLS handshake · DNS resolution · DNS timeout · Connection timeout · Read timeout · Redirect chain · Redirect loop · 301 redirect · 302 redirect · 307 redirect · 308 redirect · 304 response · 404 response · 410 response · 429 response · 500 response · 502 response · 503 response · 504 response · HEAD request · GET request · Content type · MIME sniffing · Content encoding · Compression · Brotli · ETag · Last-Modified · If-None-Match · Cache hit · Cache miss · Cache key · Vary header · Stale response · Stale-while-revalidate · Edge redirect · Origin bypass · Response parity · Header parity · hreflang · canonical URL · HSTS · HSTS preload list · Content-Security-Policy · CSP nonce · edge cache · cache split · cache-buster · Cache-Control · Age header · payload text share · lazy loading · 404 and 410 status codes
Questions about render-blocking resource
What is render-blocking resource?
A stylesheet or synchronous script the browser must fetch and process before it can paint anything below it. Each one adds a network round trip to the first paint; deferring scripts and inlining or preloading critical CSS are the fixes.
What does render-blocking resource not show or guarantee?
The count is measured from the delivered HTML, not from a rendered timeline.
Which area of the glossary does render-blocking resource belong to?
HTTP, edge and rendering: The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
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