"Accept-Language" header missing in http request from the browser

Question

We have come across an issue in production logs where "Accept-Language" is missing in the http request from the browser. Although I am not able to replicate it so I want to understand any valid use case where any specific browser may send a request without "Accept-Language" header.

Answer 1

Even GET / HTTP/1.0 is a valid HTTP request. You can create one from the telnet client if you wish and it will still return a result from the server!

Accept-Language is a header to aid in content negotiation and is optional. The most widely used browsers send the correct headers, but there may be corporate proxies who may be filtering such headers. You should not rely on this header being present.