Performance · Website glossary

Time to First Byte

Quick answer · What is Time to First Byte?

TTFB measures the time from a request's start until the first byte of its response arrives.

IN PRACTICE

Time to First Byte: an example

A browser waits for connection work and server processing before receiving the first response bytes.

KEEP IN MIND

TTFB is not total page-load time; images, scripts, and rendering can continue afterward.

Put the idea to work

Frequently asked questions

What is a practical example of Time to First Byte?

A browser waits for connection work and server processing before receiving the first response bytes.

Is Time to First Byte the total page-load time?

TTFB is not total page-load time; images, scripts, and rendering can continue afterward.

Which concepts should I read alongside Time to First Byte?

Latency: The delay between initiating an operation and receiving a response or result.
Largest Contentful Paint: LCP reports when the largest eligible visible content element in the initial viewport is rendered.