What is a full specification of X-Forwarded-Proto HTTP header?

Question

What is a full specification of X-Forwarded-Proto HTTP header values?

Answer 1

There finally is RFC 7239 - Forwarded HTTP Extension from june 2014. The header is defined in section 5.4.

Some examples:

Forwarded: proto=https
Forwarded: for=1.2.3.4;proto=http

I just hope this won't take too much time to get widely adopted. An example of the diversity of headers because of standard lacking (from here):

• X-Forwarded-Proto: https (de facto standard)
• X-Forwarded-Protocol: https
• X-Forwarded-Ssl: on
• X-Url-Scheme: https
• Front-End-Https: on