Allows you to point Firefox to your fiddler instance if it doesn't refresh the proxy settings after Fiddler has started.

What is FiddlerFox?

'FiddlerFox' is a Firefox extension that rectifies a common issue with Firefox and Fiddler's interaction. Firefox uses its own proxy settings rather than refreshing them according to the system, causing issues when Fiddler is started after Firefox. FiddlerFox solves this issue by allowing users to enable Fiddler proxy from within Firefox itself. After installation, clicking on FiddlerFox's icon on the Firefox toolbar will direct Firefox to use the Fiddler instance at port 8888 for web connections.

Stats date:
Users: 802 ▼ -7
Rating: 4.90 (10)
Version: 1.0 (Last updated: 2021-04-09)
Creation date: 2017-10-18
Weekly download count: 16
Firefox on Android: No
Manifest version: 2
  • proxy
  • *://*/*
  • webRequest
  • storage
Size: 11.85K
Email: Click to see
URLs: Website
Risk impact: High risk impact
Risk likelihood: Low risk likelihood

Other platforms

Not available on Chrome
Not available on Edge

This Firefox extension allows you to enable the Fiddler proxy from within Firefox. Because Firefox uses its own proxy settings, if Fiddler is started after Firefox is started, Firefox does not use Fiddler. This extension works around that: Once Fiddler is started you press the button in the toolbar and Firefox will then use Fiddler.

What problem does it solve? Firefox uses its own proxy settings instead of the OS-native proxy settings. The proxy settings from the OS are loaded when Firefox starts, but never refreshed afterwards. This poses a problem when you start Fiddler after you start Firefox. When Fiddler is enabled, it modifies the system proxy settings so that Fiddler is used as a proxy. Firefox does not notice this change, and keeps using whatever proxy was configured when it started.

Until this extension was developed, you needed to fiddle with the proxy settings buried deep in the Firefox menu, or restart the browse which is quite annoying during development with numberous of tabs and windows open.

What's up with FiddlerHook? Fiddler installs FiddlerHook, a local Firefox extension for detecting the presence of Fiddler and automatically enabling direction to Fiddler.

This extension is however not signed (causing issues) and is a "legacy" XPCOM extension which will be unusable from Firefox 57 onwards.

How does it work The extension works quite simple, once installed from Mozilla Add-ons, you get an icon in the toolbar of Firefox.

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User reviews
User reviews summary
These summaries are automatically generated weekly using AI based on recent user reviews. Firefox Browser Add-ons does not verify user reviews, so some user reviews may be inaccurate, spammy, or outdated.
  • Easy to use
  • Time saving
  • Directly configures Fiddler
    Most mentioned
    • Fiddling
    • Button
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    Risk impact

    FiddlerFox is risky to use as it requires a number of sensitive permissions that can potentially harm your browser and steal your data. Exercise caution when installing this add-on. Review carefully before installing. We recommend that you only install FiddlerFox if you trust the publisher.

    Risk likelihood

    FiddlerFox has earned a fairly good reputation and likely can be trusted.

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