OK, I have two different web servers serving the same html content. When I look at the developer console of the browser, I see Accept-Encoding request header is different for each, “gzip, deflate” and “gzip, deflate, br, zstd”. I know that one of the servers has brotli compression enabled but how does the browser know that in advance?

OK, I have two different web servers serving the same html content. When I look at the developer console of the browser, I see Accept-Encoding request header is different for each, “gzip, deflate” and “gzip, deflate, br, zstd”. I know that one of the servers has brotli compression enabled but how does the browser know that in advance?