Configure mobile proxies in Firefox using built-in settings, the FoxyProxy extension for profile switching, or advanced about:config options.
Unlike Chrome, Firefox has native proxy settings with full authentication support. No extension required for basic usage.
Or type about:preferences#general in the address bar and scroll to Network Settings
Configure how Firefox connects to the internet
This opens the Connection Settings dialog
When you visit any website, Firefox will prompt for your proxy credentials. Check "Remember" to save them for the session.