Like for example brotli, as being implemented in Firefox now.
5.4 SPDY
5.5 auth= in URLs
5.6 Refuse "downgrade" redirects
+ 5.7 More compressions
6. TELNET
6.1 ditch stdin
Consider a way to tell curl to refuse to "downgrade" protocol with a redirect
and/or possibly a bit that refuses redirect to change protocol completely.
+5.7 More compressions
+
+ Compression algorithms that perform better than gzip are being considered for
+ use and inclusion in existing browsers. For example 'brotli'. If servers
+ follow along it is a good reason for us to also allow users to take advantage
+ of this. The algorithm: https://github.com/google/brotli The Firefox bug:
+ https://bugzilla.mozilla.org/show_bug.cgi?id=366559
+
6. TELNET