Time to First Byte (TTFB)
Time to First Byte (TTFB) measures how long it takes a browser (or crawler) to receive the very first byte of response data after requesting a page — essentially, server response speed before any actual page content even begins loading.
Updated
November 12, 2026
Category
SEO Glossary
TTFB is foundational because every other loading metric — including Core Web Vitals like Largest Contentful Paint — starts its clock only after TTFB completes, which means a slow server response time puts a hard floor under how fast a page can possibly load, no matter how well-optimized the front-end code and images are. Common causes of slow TTFB include inadequate server or hosting resources, unoptimized database queries (especially common on dynamic CMS platforms rendering pages on every request), lack of caching, and geographic distance between the server and the visitor without a content delivery network to reduce that latency. TTFB under roughly 200-800ms is generally considered good depending on the specific benchmark used; consistently higher than that is worth investigating at the hosting and server-configuration level before focusing on front-end optimizations.
Example
A WordPress site with an unoptimized database and no caching plugin shows a 1.4-second TTFB — adding a caching layer and optimizing slow database queries cuts it to 300ms, improving every downstream loading metric as a result.
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