I have the problem that for recent pages the firefox network monitor seems to be non-functional. I give an example to make my statements clear: enter image description here

You see 3 (!) selected requests. I cannot select only one of them. If I click either, all three are selected. Further, only the first one has a status code icon (200 in this case), the others seem to have neither size nor type.

I assume this is some modern extension of the HTTP standard that allows multiple requests per connection.

However, this causes a big chunk of trouble if you want to debug things: the right panel is always showing the details of the first request. In the example above I have not found a way to inspect the (selected) POST request with all its data as well as the returned data for all three requests.

Can you please explain to me

  • What causes the combination of the requests?
  • How can I inspect the details of the different requests if possible at all?
  • 1
    It's called "pipelining", and it's enabled by default in Firefox, more or less. Only way to prevent that is to force Firefox into working under a single process, UI, painting and all under the same roof. Not an easy feat in recent versions, that tend to ignore the user's will to limit overhead, both in ressources and bandwidth. That, and the fact that your copy of Firefox probably audits all links in any given webpage in case you'd want to click on "Contact us" at the bottom of home page of a website you'll visit once in your life...
    – user1019780
    Mar 31, 2020 at 6:18
  • I am less concerned about the fact that firefox wants to be smart. It is more a debugging problem I had recently multiple times when I needed to look into the HTTP streams. Mar 31, 2020 at 7:53
  • I understand, but it's the nature of the beast: Firefox mutliplies HTTP/S requests, as do all other browsers, to speed things up for the end-user. Most servers accept a moderate number of requests from a given IP or IP range, and treat them accordingly by caching content over the first request, and ignoring the others unless content has been dynamically changed (live forms, mostly). Most browsers tend to drop additional requests once the content has been served, but in some cases, closing the extras takes some time.
    – user1019780
    Mar 31, 2020 at 8:15
  • For the record: this is now being tracked as bug at Mozilla: bugzilla.mozilla.org/show_bug.cgi?id=1628162
    – knittl
    May 6, 2020 at 10:53


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