Response Time Checker / Glossary
TTFB (time to first byte)
The time from the start of the request until the first byte of the response arrives. It includes DNS, the connection, TLS and the server's own work, so it is the earliest point at which a browser can start rendering.
How we measure it
Three cold requests one after another from our probe, each with its own DNS lookup, connection and TLS handshake; we report the median and every phase separately.
What good looks like
Our bands: excellent under 200 ms, good under 400 ms, fair under 800 ms, slow above. Google's field threshold for real users is 800 ms (good) and 1,800 ms (poor) at the 75th percentile.
How to improve it
- Cache HTML at a CDN close to visitors.
- Reduce server time (page and object caches, slow queries).
- Cut redirects before the final page.
- Use TLS 1.3 and HTTP/2.
Measure your site
Three cold samples, every phase, and a diagnosis of what is slow.
Open the Response Time Checker