Fiddler Ideas

The free web debugging proxy for any browser, system or platform.

Make sure that filters apply to MS telemetry calls (e.g.

Microsoft telemetry calls to bypass the filters and add noise. If my filter says only show localhost, I don't expect to see calls to 

  • Guest
  • Jan 16 2018
  • Under review
  • Attach files
  • Eric Lawrence commented
    January 16, 2018 22:47

    Where specifically did you set the filter? If you right-click the Session and choose "Properties", what are the flags on the unexpectedly-visible Session?

    (By default, Fiddler doesn't hide sessions which resulted in HTTP Protocol Violation errors).

  • Dave Carlson commented
    January 25, 2018 20:22

    My host is slightly different:  I tried setting up a "Hide if URL contains" and "hide following hosts", but it still shows up.  I also tried adding a line in the custom rules file, but it still powers through.

    It is a protocol violation: "ProtocolViolationInRequest".

    Is there a special way I can block this specific request?

  • Dave Carlson commented
    January 25, 2018 20:22

    By block, I mean hide from the list.

  • Eric Lawrence commented
    January 29, 2018 16:41

    In the Session's Properties, you can see what exactly the protocol violation in the request is; depending on what the problem is, it reflects either a bug in the client (likely) or something that could be fixed in Fiddler.

    To cause a Session to be hidden regardless of protocol errors, you can add the word "STEALTH" to the UI-HIDE value, e.g.


    if (oSession.urlContains("")) { oSession["ui-hide"] = "STEALTH-boring boring boring...."; }
  • Rainer Koschnick commented
    February 06, 2018 09:48

    STEALTH doesn't work for me, those requests still show.

  • Eric Lawrence commented
    February 19, 2018 13:16

    Regarding the claim that "Stealth" doesn't work-- the most likely explanation is that you either wrote the rule incorrectly, or put it in the wrong place. Feel free to email me a SAZ capture demonstrating your issue. bayden at gmail dotcom.

  • James Brooks commented
    February 21, 2018 00:34

    I am also having issues with in Fiddler. My filter is on and set to "Show only the following Hosts" -- "localhost" yet I see both localhost and  I can right click on it and choose "Filter Now --> Hide v10.vort... yet after a few captures, it starts showing v10 again.  Always with 408 request body incomplete.

  • James Brooks commented
    February 21, 2018 00:41

    As a side note. Under "Filters" --> "Hide if URL contains" -->  does work in hiding it from Fiddler

  • James Brooks commented
    February 21, 2018 00:53

    Nope, spoke to soon. Adding "Hide if URL contains" did not work. Sorry.

  • Gunnar S commented
    March 08, 2018 16:08

    The problem identified by James Brooks is driving me nuts. There must be a way to stop this from showing up in Fiddler:


    HTTP/1.1 408 Request body incomplete
    Date: Thu, 08 Mar 2018 16:01:58 GMT

  • Greg Woods commented
    March 15, 2018 10:22

    My sessions list is being filled with Windows 10 telemetry calls, all with 408 errors. Even trying to remove them using fiddler script (a workaround) has failed.

    Quote: "(By default, Fiddler doesn't hide sessions which resulted in HTTP Protocol Violation errors)."


    if I have filters enabled, nothing should bypass those filters... it's just bad manners.


  • Ed Eaglehouse commented
    March 22, 2018 13:00

    I tried adding the ui-hide member on the session in the OnBeforeResponse handler using Eric's STEALTH suggestion. Fiddler threw a compilation error, "Objects of type 'Fiddler.Session' do not have such a member."

    Using automatic syntax completion and comparing other code in CustomRules.js, the urlContains function was apparently renamed uriContains. Fiddler didn't complain after I used the latter function name.

    I agree with Greg Woods' comment about filters actually filtering what you tell them to. Perhaps an additional UI option to show/hide protocol violations would be in order.

  • Ed Eaglehouse commented
    March 22, 2018 14:04

    20 minutes later, STEALTH isn't working for me, either. The telemetry responses are still showing up.

  • Greg Woods commented
    March 22, 2018 15:20

    An example of the amount of crap filling my fiddler sessions

  • Steven Lamport commented
    April 22, 2018 16:04

    I have the same issue and it drives me crazy. I have tried just about everything but these still show.

  • Bruno Amancio commented
    May 15, 2018 15:50

    Same shit for me. I couldn't find a way to solve it yet.

  • Eric Lawrence commented
    May 15, 2018 20:29

    Okay, I spent a few minutes looking at this.

    > if I have filters enabled, nothing should bypass those filters... it's just bad manners.

    Fiddler's filters deliberately ignore cases where there's good reason to believe that something has broken that might not be failing without Fiddler in the way. Otherwise, running Fiddler could cause side-effects that would be nearly impossible to troubleshoot.

    Now, unfortunately, because of how stealth is implemented, it's not applied to cases where there's a protocol violation in the Request or Response. The test in the ShouldBeHidden function probably should be changed to respect stealth because it's a non-default override.

    As a user, to make these lines go away, you could either change Tools > Fiddler Options > General > "If protocol violations are observed" to "Do Nothing" (which is sad, because protocol violations ARE generally very useful), or you could possibly write code that masks out the SessionFlags.ProtocolViolationInRequest flag on requests you don't care about. Or you could hack together code that just hides them periodically. (eww).

    The script sample earlier has two typos-- the function is named uriContains and the word stealth needs to be in lowercase.

    For best results, put it inside OnPeekAtRequestHeaders:

    if (oSession.uriContains("")) { oSession["ui-hide"] = "stealth-boring boring boring...."; }
  • ss ss commented
    May 17, 2018 09:17

    Would love to get this fixed. None of the suggestions fix this, or at least need better explanations, I was unable to get onpeekheaders to do fuck all.

  • Greg Woods commented
    May 29, 2018 11:14

    >or you could possibly write code that masks out the SessionFlags.ProtocolViolationInRequest flag on requests you don't care about.

    My point was that fiddler already knows about "requests I don't care about"...these are in the Filters., so it seems logical that fiddler applies filter rules to protocol violations

    For now I have ignored all protocol violations, editing OnPeekAtRequestHeaders resulted in everything being filtered out. Probably something I did wrong, but I haven't time to investigate at the moment.

  • Guest commented
    August 03, 2018 13:00

    This can be done in the fiddler script editor, just dont display sessions where the hostname contains "vortex"

  • Brian Lacy commented
    November 17, 2018 16:04

    Exactly the same problem here. These "vortex" violations make fiddler next-to-useless -- or at least, makes Filtering useless, because you still can't focus on the items you're trying to focus on.

    I'm setting Protocol Violations to "Do Not Show" -- but at the very least, this option should be present IN the Filters pane, as part of the Filter config, so there's some clue as to how to accomplish what you're actually there to do in the first place.