Fiddler Ideas

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Fiddler Crashes

This happens a lot. I decrypt HTTPS and I filter by URL. I connect to intranet as well as internet hosts. No real reproduction steps, sorry.


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Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at

Object reference not set to an instance of an object.

Type: System.NullReferenceException
Source: Fiddler
at Fiddler.ServerChatter.<>c__DisplayClass3.<RunConnectionStateMachine>b__1(Object s, EventArgs oEA)
at Fiddler.Session.FireCompleteTransaction()
at Fiddler.Session.set_state(SessionStates value)
at Fiddler.Session.ReturnResponse(Boolean bForceClientServerPipeAffinity)
at Fiddler.Session.RunStateMachine()
at Fiddler.ServerChatter._smNotifyCSMDone()
at Fiddler.ServerChatter.RunConnectionStateMachine()
at Fiddler.Session.RunStateMachine()
at System.Threading._ThreadPoolWaitOrTimerCallback.PerformWaitOrTimerCallback(Object state, Boolean timedOut)

Fiddler v2.6.2.3 (x64 AMD64) [.NET 2.0.50727.5485 on Microsoft Windows NT 6.1.7601 Service Pack 1]

  • Guest
  • May 23 2016
  • Under review
  • Attach files
  • Guest commented
    23 May, 2016 06:56am

    I can leave the error dialog open and Fiddler will keep running and doing its thing. Once I click on "OK", Fiddler shuts down.