TTFB
Time to first byte: how long a server takes to begin answering.
What TTFB does not show
It is the speed measurement that matters most to a crawler, because a crawler that times out records nothing at all.
Where TTFB comes up on this site
- Core Web Vitals without CrUX: field data for small sitesCollecting your own field data Google's open-source web-vitals library reports LCP, INP and CLS, plus TTFB and First Contentful Paint, from real page views in any modern browser.
- Analytics added 650 ms to every request: how we found itA second of TTFB on a mostly static page is not an image, font or rendering problem.
Related terms in Delivery and rendering
What arrives on the wire, and what only exists after something else runs.
broken embed · payload ratio · render dependence · render dependence gap · edge cache pinning · Core Web Vitals · CrUX · field data · prompt injection · Hydration mismatch · Dynamic rendering · DOM depth · Edge transformation · 202 interstitial · rate limiting · bot management platform
Questions about TTFB
What is TTFB?
Time to first byte: how long a server takes to begin answering.
What does TTFB not show or guarantee?
It is the speed measurement that matters most to a crawler, because a crawler that times out records nothing at all.
Which area of the glossary does TTFB belong to?
Delivery and rendering: What arrives on the wire, and what only exists after something else runs.
← edge cache pinning · Core Web Vitals →
See it in the full glossary · 772 terms across 19 areas.
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