What is TTFB (Time to First Byte) value and how do you test for it?

Question

What is TTFB (Time to First Byte)? 

TTFB is the initial server's response time, which is the time between a web browser requesting a website and when the website starts to load from the server.

A high TTFB can make your site seem slow when, in fact, the first connection is taking a bit of time.

Answer

If you would like to know what your TTFB time is to your website, there are some methods you can use.

*** This information is provided so you can have a measure of the initial server response time. ***

We will use 'cptest-2.com' as our example.

Example Command (by command-line):

curl -o /dev/null -w "Connect: %{time_connect} TTFB: %{time_starttransfer} Total time: %{time_total} \n" cptest-2.com

Example Output:

 % Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 234 100 234 0 0 562 0 --:--:-- --:--:-- --:--:-- 562
Connect: 0.349885 TTFB: 0.415894 Total time: 0.416210

You can also find the TTFB value by using a modern web browser. Most browsers contain a 'Developers Tools' section. 

In the screenshots, you can see the TTFB value is the value of 'Waiting'.

Chrome Example:

FireFox example:

You may also use a third-party site like GTmetrix to analyze your site to give you the TTFB value.

Most TTFB bits should be in the millisecond range depending on your network configuration.

Related support articles:

My site's TTFB (Time To First Byte) is high only when accessing PHP content

Why is my Time To First Byte high?