---
title: time.to_first_byte
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/variables/client-response/time-to-first-byte
---

**Type:** RTIME  
**Access:** read-only

**Available in:** deliver, log

The time interval since the request started up to the point before the
`vcl_deliver` subroutine ran. When used in a string context, an RTIME variable like
this one will be formatted as a number in seconds with 3 decimal digits of
precision. In `vcl_deliver` this interval will be very close to
`time.elapsed`. In `vcl_log`,
the difference between time.elapsed
and `time.to_first_byte` will be the time that it took to send the response body.