Backend Time /Frontend Time Metrics

I work on a site that has a lot of backend data and I’d like to be able to figure out the backend time vs frontend.

As I understand, the backend represents you need to look at TTFB. Looking at how it was defined in an HTTP Archive post, Patrick Meenan defined it as follows:

“To get JUST the backend time you’ll need to look at the timing for the TTFB for the base page in the requests table (TTFB at a request level is the server time). To be really accurate you’d also want to subtract the socket connect time to allow for the network RTT on the request which is included in the TTFB.”

QUESTION: Does the TTFB in Webpagetest represent the backend time? Or do I need to go to the Requests table and then add up the numbers? I couldn’t find the socket connection time. I don’t need a fully accurate # just an idea of %

FrontEnd time - I’m assuming that is Document Complete.

The “First Byte” shown on the WPT results table is a combination of the TTFB+DNS Time+TLS Connection time. Basically it is a combination of network overheads + backend time.

If you are interested in the back end time only, then you should be looking at the “Time to First Byte (ms)” value. You can get this in 2 ways:

  1. In the requests table, click on the first request and see the value
  2. Export the results to an excel and look for the column named “Time to First Byte (ms)”

You do mention that you are looking for “backend time vs frontend”. Could you elaborate? eg: Are you trying to see how much time was spent in downloading v/s rendering? This may help the community give you a better answer.

Yes, I’d like to compare the backend time vs frontend based on Steve Souders post here:

Question: I thought the TTFB = (DNS LOOKUP) + (INITIAL CONNECT) + (R/T)