Time to First Byte is the time between a browser starting a navigation request and receiving the first byte of the response. It includes redirects, DNS lookup, connection setup, TLS negotiation and the server's processing time. TTFB is not a Core Web Vital, but because nothing can render until the response starts arriving, a slow TTFB delays First Contentful Paint and Largest Contentful Paint.
What counts toward TTFB
In field data, TTFB covers the whole wait from navigation start, so redirects count, as does connection setup. Lab tools sometimes report only server response time. Know which definition a tool uses before comparing numbers.
- Redirects before the final URL
- DNS lookup
- TCP and TLS connection setup
- Server processing: database queries, rendering, API calls
- Network time for the first byte to travel back
What good looks like
web.dev suggests a TTFB of 0.8 seconds or less at the 75th percentile of page loads as a rough guide for most sites. It is guidance rather than a pass or fail threshold, because sites that render on the client can have a fast TTFB and still be slow to show content.
How to improve it
Serve HTML from a CDN cache or static files where you can. Speed up server rendering by caching data and avoiding slow API calls in the request path. Remove redirect hops, especially on links from ads and emails. Use modern protocols such as HTTP/2 or HTTP/3, and consider 103 Early Hints so the browser can start fetching critical assets while the server prepares the page.
Example
A slow pricing page
Ploughstack's pricing page queries three internal services on every request to build plan tables. Field data shows a much higher TTFB than the rest of the site. Moving the plan data into a cached file rebuilt when pricing changes removes the calls from the request path, and the page's TTFB drops in line with other pages.
Common mistakes
Ignoring redirect hops
A link through http to https to www adds round trips before the real page request begins.
Testing only from your own region
TTFB varies by distance. Check field data across countries, not just a lab test near your server.
Questions
It is not one of the Core Web Vitals Google uses in its page experience guidance. It matters because it affects LCP, which is.
