Time to First Byte (TTFB) is the duration between a browser sending an HTTP request and receiving the very first byte of the server's response — a measurement of server responsiveness that sits upstream of all visible page rendering. TTFB captures three cumulative delays: DNS resolution time (looking up the domain's IP address), TCP/TLS connection setup time (the handshake between browser and server), and server processing time (the time PHP, the database, and caching layers need to generate the response). Google considers a TTFB under 800 milliseconds "needs improvement," with 200 milliseconds or below considered fast. For WordPress sites, the dominant driver of slow TTFB is server processing: a non-cached PHP request that queries the database multiple times can take 800ms–2s. The most impactful fixes are full-page caching (serving pre-built HTML without running PHP), a faster hosting tier, and an edge CDN that serves cached responses from a server geographically close to the visitor.
Glossary entry