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🚀Fiddler add-on to cache API responses.
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🚀 Nitro Cacher

Fiddler add-on to cache API responses based on rules.

Useful while developing in projects that

  • Use rate-limited APIs.
  • Use a lot of API calls that are cached in-memory/in-process in production which gets invalidated between recompiles in your workstation.

An out-proc/disk cache baked into the application is probably the right solution to these problems. But chances are that you are already using Fiddler for debugging API calls, and this add-on provides a cheap and re-usable alternative for caching API calls in your development machine without needing you to change a single line of your project's code.


  • Match URL using various criteria: Exact, Partial, Regex, Host Name.
  • Options to mark sessions served from cache in UI with colors, or hide it.
  • Enable/Disable the cache for individual rules or as a whole.
  • Group rules into profiles, and switch between profiles at any time.
  • Reset cache per rule, per profile or as a whole.


Download the NitroCacher.dll from releases, and

  • Copy to \Documents\Fiddler2\Scripts to make the extension available to the current user.
  • Copy to \Program Files\Fiddler2\Scripts OR AppData\Local\Programs\Fiddler\Scripts (this path depends on how fiddler was installed) to install for all users

Restart fiddler, and navigate to Nitro Cacher tab for configuring rules.

Configuration Screens

Main Screen

Main screen image

Rule configuration

Rule configuration image


Bug reports and Pull Requests are welcome. The add-on is not thouroghly tested, and could use some improvements in terms of code and features. Few features that are planned:

  • An installer
  • Persistant cache
  • Filter requests further using HTTP verbs
  • Expiration and Cache size limit for the cache.
  • Display Summary of cache (Number of items, memeory used etc.)


  • Checkout the code
  • Open NitroCacher.sln in Visual Studio
  • Edit the Post Build event to point to <fiddler installation path\Scripts> where the add-on should be copied to.
  • Update references to fiddler.exe with the correct paths.
  • Build.
  • Launch fiddler to test the add-on. Every recompilation needs fiddler to be closed and opned again to reload the add-on.
  • Attach Visual Studio to the Fiddler.exe process for debugging.
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