At my previous job I was responsible for the i18n of our globally-used web app. The problem came down to a choice: follow the HTTP standard and pay attention to

At my previous job I was responsible for the i18n of our globally-used web app. The problem came down to a choice: follow the HTTP standard and pay attention to the request header the browser sends that specifies its language setting, or ignore the browser and maintain a user configuration setting in our app. We chose the latter, which worked much better: users could choose a language from a dropdown at any time, and we remembered that choice across sessions. (They had to log in to the webapp so we knew who they were, but we also set a cookie so most of the time the login page was the right language too.) I guess the other choice we made was to support any language through the same codebase, rather than a separate codebase/deployment per language. A lot of websites do the latter, which means that if you go to a country-specific site you're stuck with the language used for that site. Bad design; I think there are few places left in the world where a region only has one language in common use anymore... at least among people who use the internet.