---

title: Time to first byte

slug: Glossary/Time_to_first_byte

page-type: glossary-definition

---

{{GlossarySidebar}}

**Time to First Byte** (TTFB) refers to the time between the browser requesting a page and when it receives the first byte of information from the server. This time includes [DNS](/en-US/docs/Glossary/DNS) lookup and establishing the connection using a [TCP](/en-US/docs/Glossary/TCP) handshake and [TLS](/en-US/docs/Glossary/TLS) handshake if the request is made over [HTTPS](/en-US/docs/Glossary/HTTPS).

TTFB is the time it takes between the start of the request and the start of the response, in milliseconds:

```plain

TTFB = responseStart - navigationStart

```

## See also