Should 2 different versions of a user guide use a different canonical URL?
Documentation version 1.1.0.Final:
<link rel="canonical" href="http://docs.foo.org/1.1.0.Final/index.html">
Documentation version 1.2.0.Final:
<link rel="canonical" href="http://docs.foo.org/1.2.0.Final/index.html">
Or should 2 different versions of a user guide use the same canonical URL?
Documentation version 1.1.0.Final:
<link rel="canonical" href="http://docs.foo.org/latestFinal/index.html">
Documentation version 1.2.0.Final:
<link rel="canonical" href="http://docs.foo.org/latestFinal/index.html">
Per The Canonical Link Relation from RFC 6596, the canonical link type may only be used for URIs that identify content that is
- duplicative, or
- a superset.
As this is not necessarily the case for different versions of the user guide (because features might be added/removed/changed), the canonical link type must not be used to always point to the latest version. If you want to use canonical, it would have to be self-referential.
来源：https://stackoverflow.com/questions/39913212/link-rel-canonical-should-different-user-guide-versions-use-the-same-canonica