All the big browsers do send a proper Accept-language string. It is configurable and uses OS settings as default. One can't really go wrong with that. Discover

All the big browsers do send a proper Accept-language string. It is configurable and uses OS settings as default. One can't really go wrong with that. Discovering Accept-Language was a small revelation. I had no idea on how to do the localization of a web project of mine, geo-ip sounded ridiculous to me (not configurable). And there it was, a sound solution already provided by the browser.