Time to First Byte is the time from a browser requesting a page to receiving the first byte of the response — covering DNS lookup, connection and TLS setup, the request travelling to the server, the server generating the response, and the first byte travelling back.
Definition
Time to First Byte is the time from a browser requesting a page to receiving the first byte of the response — covering DNS lookup, connection and TLS setup, the request travelling to the server, the server generating the response, and the first byte travelling back. It is not a Core Web Vitals metric itself, but it is a foundational input to LCP and overall perceived speed: every millisecond of TTFB delays everything that follows, so a slow TTFB caps how fast a page can possibly be.
TTFB is driven by server processing time (database queries, application logic, uncached page generation), hosting quality, distance between the user and the server, and redirects. A good TTFB is generally under about 800 milliseconds, and well-optimised sites are much faster.
In context
For an iGaming affiliate, TTFB is worth checking because a content site with dynamic pages (a database-backed glossary, comparison tables built from feeds, per-market rendering) can have a slow server response that undermines every downstream metric no matter how well the front end is optimised. If LCP is failing and the LCP resource itself is small and fast, a high TTFB is often the real cause.
The fixes are server- and infrastructure-side: cache rendered pages (full-page or edge caching) so most requests are served without regenerating; optimise slow database queries and application logic; use a CDN so content is served from close to the user; upgrade underpowered hosting; and eliminate redirect hops on entry URLs. For a large glossary specifically, caching the term pages aggressively (they change rarely) so they are served near-instantly is one of the highest-impact performance wins available.
TTFB should be monitored as field data and in server logs, not only in lab tests from a fast location. For affiliate-facing content, the framing is that TTFB is the time to the first byte of the response and a foundational input to LCP and perceived speed, that a good TTFB is under about 800ms, that on a content site it is usually a server-processing or hosting-distance problem, and that caching, query optimisation and a CDN are the main fixes.
Worked example
An affiliate's LCP is failing despite a small, preloaded hero image. Testing shows a TTFB of 1.4 seconds because glossary pages are generated per request from the database.
The team adds full-page caching for term pages (which change rarely) and a CDN; TTFB drops to 200ms and LCP passes without any front-end change.
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