The implementation is currently disabled in the Firefox Nightly and Beta pre-release channels and will be disabled when Firefox 88 is released on April 19, 2021. The implementation will be removed in Firefox 90. After FTP is disabled in Firefox, the browser will delegate
ftp:// links to external applications in the same manner as other protocol handlers.
With the deprecation,
browserSettings.ftpProtocolEnabled will become read-only. Attempts to set this value will have no effect.
To help offset this removal,
ftp has been added to the list of supported protocol_handlers for browser extensions. This means that extensions will be able to prompt users to launch a FTP application to handle certain links.
Please let us if you have any questions on our developer community forum.