Firefox debugger test

HTTP request method
GET
Server time
2026-09-14T16:07:16.084548+00:00

What do I do now?

  1. Point Firefox at this site’s URL and observe that “HTTP request method” in the rendered response shows “GET” as expected.
  2. Wait a few seconds then crack open the debugger.
  3. Compare the “Server time” values between original source and what’s shown in debugger.

If the server times are different this indicates the debugger made a fresh request for the page source.

  1. Close the debugger.
  2. Hit “Perform POST” and observe that “HTTP request method” in the rendered response shows “POST”.
  3. Wait a few seconds then crack open the debugger.
  4. Compare “HTTP request method” values between original source and what’s shown in debugger.

What’s this?

My attempt to demonstrate the issue described in Bugzilla bug 1890697.

What’s the problem?

Debugger should show sources as they were when the page was loaded, or not at all. Opening the debugger should not result in any new network requests (except perhaps to retrieve source maps).

The swapping of POST for GET is a definite no-no.

I work on an ancient web application which doesn’t use reusable URLs or the Post/Redirect/Get cycle. Making a second GET request to the same URL, or swapping HTTP verbs for a given URL can result in wildly different results.