Adding a URL handler to FIrefox

Support & Help Requests
1

This is a topic on which apparently a ton of outdated information is floating around - does anyone know how to register a URL handler for a new scheme (e.g. “foo://”) in Firefox, which can then be associated with an application to handle such URLs?
It has to work with current versions of Firefox (55/56). Please only respond if you have successfully done this yourself.

2

OK, I finally figured it out - this is how it works in 16.04 at least - tested with Firefox 55 and 57:

Suppose you want to associate an application that handles myprotocol://… URLs.

  • create ~/.local/share/applications/myapp.desktop which launches the app,
    similar to this (the last line is essential, as is the %u argument in Exec=):

    [Desktop Entry]
    Encoding=UTF-8
    Version=1.0
    Type=Application
    Terminal=false
    Exec=myapp.sh %u
    Name=My App
    Comment=
    Icon=
    Categories=Application;Network;
    MimeType=x-scheme-handler/myprotocol;

  • start Firefox and open about:config

  • create new boolean “network.protocol-handler.expose.myprotocol”, set to “false” (do not use “true”!)

  • open a “myprotocol://whatever” URL in Firefox

=> you should get a window asking you to associate it with the application, where you can also check a “remember this” option so you won’t be asked again next time (which will also set the flag to “true”)

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