Time to First Byte (TTFB)

TTFB measures how long from requesting a page until the first byte of response arrives. It captures server processing, database queries and network distance — everything before the browser can start rendering.

TTFB sets the floor for every other metric. Nothing renders before bytes arrive, so a 1.5-second TTFB caps how good LCP can possibly be no matter how well the front end is optimised.

High TTFB usually means slow database queries, no caching, or a server physically far from the visitor. The last is why a site hosted in one country feels slow in another, and why static generation and CDNs help so much.

Why it matters

If your site is slow everywhere rather than on particular pages, TTFB is where to look first, and it's usually a hosting or caching decision rather than a code one.

Related terms

Largest Contentful Paint (LCP)LCP measures how long until the largest visible element — usually a hero image or headline — has rendered. Google considers 2.5 seconds or less good, …CDN (Content Delivery Network)A CDN is a network of servers distributed worldwide that cache copies of a site's files and serve each visitor from the location nearest them, cutting…SSR, SSG and ISRThree ways of producing a web page: server-side rendering builds it per request, static site generation builds it once at deploy time, and incremental…

More in Web & Performance

Core Web VitalsLargest Contentful Paint (LCP)Cumulative Layout Shift (CLS)SSR, SSG and ISRCDN (Content Delivery Network)Headless CMSProgressive EnhancementWeb ApplicationTechnical Debt

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