RFC 3749 defines a mechanism for compressing a TLS connection using the DEFLATE compression mechanism. When used in conjunction with https, this fills a similar role to that of Content-Encoding: gzip, except that headers benefit from compression too (as the whole connection is compressed), and I suspect there is less chance of weird proxy / caching bugs. I decided to do some quick tests to see which browsers actually support this, as I found approximately zero information on the subject on the internet; the results, unfortunately, are rather dismal and depressing: