It's based on your browser's Accept-Language header, nothing to do with location.
(It's only a naive implementation of parsing the Accept-Language header. Sorry, was all I could do at the time.)
(It's only a naive implementation of parsing the Accept-Language header. Sorry, was all I could do at the time.)
I'm not sure what the standard says, but i suspect you'd surprise users considerably less if you used the first language listed in that header rather than the last (assuming equal or missing q values).
A proper implementation would make for a good Caddy module.
Accept-Language: en-US;q=1.0, en;q=1.0, fr-FR;q=0.5, fr;q=0.5