set_from_accept_language

The 'set_from_accept_language' directive is a feature of the NGINX Accept-Language module that allows you to derive a locale variable from the client's HTTP 'Accept-Language' header. The directive requires you to specify a variable (which should start with a '$' symbol) and one or more supported locales. When a request arrives, NGINX inspects the 'Accept-Language' header, which contains a comma-separated list of languages the client prefers. It matches these languages against the specified locales. If a match is found, the variable is set to that locale; otherwise, it defaults to the first locale in the specified list.

The directive operates in various contexts—http, server, and location—giving you flexibility in where to apply locale detection based on user preferences. The locales specified after the variable must be properly ordered as they represent the priority sequence for selection. The directive also accounts for the case where the 'Accept-Language' header may be sorted based on quality values (denoted by 'q'), although this is not guaranteed and can vary across different browsers. If no suitable match is found, the module seamlessly falls back to the first locale in the list, ensuring that every request receives a defined language output.