Firefox/protocols

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Adding a New Protocol

Status: worked up until 99.0.1 under Ubuntu 22.04; does still work in LibreWolf 99.0.1-4. Possibly an issue with the Snap migration?

To add a new protocol -- e.g. wooz:// -- you add the following entries to about:config:

network.protocol-handler.app.<protocol> = <path to executable>
network.protocol-handler.expose.<protocol> = false
network.protocol-handler.external.<protocol> = true

...where in this case <protocol> would be wooz.

The value of the first line may be arbitrary, as Firefox will let you browse for the executable to use when handling a link.

(To add an item to about:config, search for it. The UI will give you the option to add or modify. [1])

Protocol handlers appear in Settings (about:preferences) under "Applications", and can be edited or deleted from there.

Links

Reference

• MozKB:
  • Register protocol: instructions for various versions of Firefox under different OSes, but doesn't explain what the config entries do
  • network.protocol-handler.app.(protocol): main article
  • network.protocol-handler.expose-all: setting this FALSE may result in Firefox asking permission to load "https" links on a per-domain basis, which isn't generally what we want.
  • network.protocol-handler.expose.(protocol)

Posts

• 2017-07-30 I want to register a custom protocol handler in Firefox/Linux @Mozilla Support