Last year, the Firefox platform development team announced plans to remove the built-in FTP implementation from the browser. FTP is a protocol for transferring files from one host to another.
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.
Most places where an extension may pass “ftp” such as filters for proxy or webRequest should…