I can think of three scenarios Tor Browser in which Tor Browser might set the language automatically (however there are probably more): - On installation, Tor Browser should set the user's language to match their system language - When the user changes their system language, Tor Browser will ???? - When the user updates from a single-locale to multi-local build, Tor Browser will ???? When it sets the language automatically we'll probably want to inform the user what has happened, and deeplink to the Language section in `about:preferences#general` to override the setting if desired.