RFC 7240, "Prefer Header for HTTP", June 2014Source of RFC: IETF - NON WORKING GROUP
Area Assignment: app
Errata ID: 4955
Reported By: Vasiliy Faronov
Date Reported: 2017-03-01
Section 2.1 says:
It should say:
"Prefer: Lenient" is a valid header that specifies an (unregistered) preference named "lenient" with an empty value.
On the other hand, this document defines a preference named "handling", which can take the value "lenient" to indicate lenient processing, which is the stated intent of this example.
There is no provision for specifying a preference by its *value*, as opposed to by its *name*.