One of my Firefox extensions, specifically, one called FiddlerHook, is currently disabled and has no remove button. It has a note that it's unverified, so I want to remove it, but there is no Remove button. How do I go about removing it?

Following the instructions given in this answer, I went to my extensions folder to delete it that way, but about half of the extensions there are represented by GUID names. Since FiddlerHook isn't among the ones that I can see among the more plain text names, I'm assuming that it's one of the GUID ones, but I don't want to delete the wrong one. I tried loading one of them into a text editor, and it looks as though they're executables of some kind (I saw PK followed by a bunch of gibberish), so that didn't help me figure out which one it is I have to delete.


Taking SleepingGod's advice, I went to the official documentation, and that said that there should be a .xpl file or a filder with the same name as the extension's ID. In the case of FiddlerHook, that ID is [email protected], but there's no [email protected] file or [email protected] folder in my extensions folder. A thorough search of my entire C drive also came up empty. Restarting Firefox in safe mode was of no help, because even in that mode, that extension doesn't have a remove button in the Extensions Manager.

Would there be anything in the registry that would be causing that extension to show up as an entry in the Extension Manager even though there is no .xpi file for it?

  • 1
    Firefox extensions (.xpi files) are ZIP files. Simply because it's non-text (gibberish) doesn't mean executable; it just means not text, AKA a binary file. You can examine the contents using any ZIP file viewer (WinZIP, PKZIP, 7Zip, etc.).
    – Ken White
    Apr 27, 2017 at 2:34
  • 1
    support.mozilla.org/en-US/kb/… What have you tried of the official documentation? Apr 27, 2017 at 4:15
  • "PK " in the first two bytes corroborates @KenWhite. Windows explorer supports ZIP natively, so it is a simple matter of diving into the ZIP files.
    – Yorik
    Apr 27, 2017 at 16:43
  • @KenWhite I assumed that it was an executable, because executables have two specific recognizable text characters followed by the rest of the file, and these fit that pattern. I didn't realize that ZIP files also fit that pattern.
    – RobH
    Apr 27, 2017 at 16:44
  • @Yonk You'd have to change the .xpi extension to .zip to allow Windows Explorer to dive into them. As is, it just shows them as an unassociated file type.
    – RobH
    Apr 27, 2017 at 16:48

1 Answer 1


I finally managed to solve my problem. Even though FiddlerHook was nowhere to be found in the Extensions folder, it was still listed on the Extensions page.

After searching for its ID in the registry (found by going to the Troubleshooting Information page in the help menu -- thanks to @fixer1234 for pointing that page out), I found it under HKLM/SOFTWARE/Wow6432Node/Mozilla/Firefox/Extensions. Deleting that key removed its entry in the Extensions page.

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