Google has recently updated its documentation regarding rel canonical annotations, aiming to provide users with a clearer understanding of how Google interprets these annotations. It's important to note that these updates don't signify any alteration in Google's approach to handling rel=canonical annotations but rather serve to articulate the existing processes more explicitly.

Understanding Canonical Link Relation – RFC 5988

Google has consistently referred to RFC 5988 as the benchmark for its utilization of the canonical link relation. This RFC, established by the Internet Engineering Task Force (IETF), sets forth standards for various Internet and networking technologies, particularly those pertaining to the HTML rel link attribute.

In simpler terms, an HTML element can be thought of as a fundamental component of a webpage, which can be enhanced with attributes. In this context, the Link element is augmented by the Rel attribute.

RFC 6596 delineates the rel link attribute as follows:

RFC 5988 specifies a method for defining relationships between links on the web. This document introduces a new category of such a relationship, 'canonical,' to denote an Internationalized Resource Identifier (IRI) as the preferred option over resources with duplicated content.

Typical applications of the canonical link relation include specifying the preferred version of an IRI among duplicate pages created with the addition of IRI parameters (e.g., session IDs) or indicating the single-page version as preferred over the same content divided across multiple component pages.

In essence, the canonical link element indicates when another document is duplicative and designates the preferred original. These principles serve as the foundation for Google's handling of the canonical link element.

Updates to Canonical Documentation

The revisions made to the Search Central Documentation primarily focus on rel=”canonical” link annotations beyond scenarios involving duplicative documents, alongside some minor adjustments to the page.

One notable change is in the following sentence:

“Google supports rel canonical link annotations as described in RFC 6596.”

This has been modified by adding the term 'explicit':

“Google supports explicit rel canonical link annotations as described in RFC 6596.”

Though seemingly minor, this alteration underscores that Google adheres closely to the standards outlined in RFC 6596.

Furthermore, a new paragraph has been introduced:

“rel=”canonical” annotations that suggest alternate versions of a page are ignored; specifically, rel=”canonical” annotations with hreflang, lang, media, and type attributes are not used for canonicalization.

Instead, use the appropriate link annotations to specify alternate versions of a page; for example, link rel=”alternate” hreflang for language and country annotations.”

In essence, this advises against using “canonical” to denote attributes such as different languages or media types, suggesting the use of “alternate” instead.

It's crucial to note that these updates do not signify a change in Google's treatment of canonical or alternate link elements.

Google's changelog documentation provides further insight:

“Clarifying the extraction of rel=”canonical” annotations
What: Clarified that rel=”canonical” annotations with certain attributes are not used for canonicalization.

Why: The rel=”canonical” annotations help Google determine which URL of a set of duplicates is the canonical. Adding certain attributes to the link element changes the meaning of the annotation to denote a different device or language version. This is a documentation change only; Google has always ignored these rel=”canonical” annotations for canonicalization purposes.”

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