Response Time Checker / Glossary
Cold and warm requests
A cold request starts from nothing: DNS lookup, TCP connection and TLS handshake before the request itself. A warm request reuses an open connection and skips all three, so only the server's work and the transfer remain.
How we measure it
Our three samples are cold on purpose: that is what a first-time visitor, or a visitor whose connection closed, experiences.
What good looks like
Cold TTFB in the good band; warm requests close to the server time alone.
How to improve it
- Everything that shortens DNS, connection and TLS helps cold requests; caching and server work help both.
Measure your site
Three cold samples, every phase, and a diagnosis of what is slow.
Open the Response Time Checker