> Both formats are supported by the absolute majority of web browsers [...]. Unfortunately this isn't true. IE still does not support deflate as specified in t

> Both formats are supported by the absolute majority of web browsers [...]. Unfortunately this isn't true. IE still does not support deflate as specified in the RFC, with a zlib header. It only supports raw deflate. https://www.ietf.org/rfc/rfc2616.txt https://www.ietf.org/rfc/rfc2616.txt deflate The "zlib" format defined in RFC 1950 [31] in combination with the "deflate" compression mechanism described in RFC 1951 [29]. This has lead to most browsers also accepting raw deflate, to be reverse compatible.