I've been testing adding my own mailto: protocol handlers as tests for my webmail. Unfortunately I'm not sure how to remove the test protocol handlers. This is explicitly not the same thing as disabling the handler, I simply want to remove the tests handlers.

I have looked in about:config in Firefox and I've looked in the Windows Registry just to cover the bases I'm familiar with. Where are the protocol handlers stored for Firefox so I can delete the test handlers?

1 Answer 1


In the Mozilla Firefox application data folder the protocol handler preferences (I'm using Firefox 24 ESR) is stored in an editable text file named mimeTypes.rdf.

To access Firefox profiles go to Start/Run and type %appdata%\Mozilla\Firefox\Profiles.

Removing an entry unfortunately requires restarting Firefox for the protocol handlers to be removed when looking at protocol associations such as mailto: in Options/Applications.

  • 1
    An easier way to get to the profile folder is to click the Help button in Firefox, then click "Troubleshooting Information," then click the Show Folder button. Be sure to close Firefox before editing or deleting the mimeTypes.rdf.
    – trlkly
    Jun 25, 2014 at 16:45

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