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Even after closing the Fiddler application, the instance of the process is still running

Even after closing the Fiddler application, the instance of the process is still running and when I try to start Fiddler a second time, it shows prompt telling Fiddler is already running and do you want to start fiddler any way. 

If we choose Yes, then it will give another prompt telling port is in use and shall use random port.


This issue is coming only after upgrading the Fiddler to the latest version from the site 4.6.3. Older versions were fine.

  • Guest
  • Dec 9 2016
  • Will not implement
  • Attach files
  • Aaron Roberts commented
    8 Jun, 2017 01:37pm

    This started happening for me when I enabled the 'Participate in the Fiddler Improvement Program."  Disabling this feature resolved the issue.

  • Guest commented
    19 Apr, 2017 06:56am

    As per Tsviatko Yovtchev comment, the issue seems to be resolved.

    Uninstall the current fiddler and install the new version. Seems to be working fine.

  • Deleted User commented
    8 Mar, 2017 05:44pm

    This issue is caused by Fiddler Script Editor and happens only in pre-2017 versions of Fiddler. The 2017 version should not exhibit this problem. A clean install including removing any old FSE installs is needed though. Please, note that 2017 version of Fiddler include FSE and it is not available as a separate add on any more. Please, do not install any old versions of FSE add on on top of 2017 Fiddler.

  • Guest commented
    17 Feb, 2017 09:52am

    same here as described in the first comment

  • oli fozzy commented
    2 Feb, 2017 01:24pm

    Same problem here.

    I already try with a clean un-install, and reinstall . 


  • Eric Lawrence commented
    24 Dec, 2016 07:30pm

    How long does the problem persist? Do you have the option to "Remove certificates on exit" enabled if you click the Tools > Fiddler Options > HTTPS > Certificate generator configuration link?

  • Guest commented
    14 Dec, 2016 09:51am

    No extensions installed. Just did an installation of the latest over the existing installation of older version.

  • Eric Lawrence commented
    9 Dec, 2016 04:13pm

    I've seen this happen once in a while too. Do you have any extensions installed?