In short. A canonical URL is the preferred address for duplicate content, while Google selects its representative using declarations and other signals.
Definition: A canonical URL is the preferred web address for content available at multiple addresses. A website can declare that preference; in Google Search, the canonical URL is the representative address Google selects for a group of duplicate pages.
Key facts
- As of 17 October 2026, Google's canonicalization documentation explains that Google can select a different canonical from the website's preference.
- Google's implementation guidance treats redirects and
rel="canonical"annotations as strong signals; sitemap inclusion carries less weight. - The canonical link specification requires the target to contain duplicate content or all the referring page's content.
- Google's URL Inspection documentation locates canonical selection in the indexed-page report.
How does a website declare a canonical URL?
A canonical link is an HTML element that identifies the preferred address through rel="canonical". The IETF's RFC 6596, The Canonical Link Relation, published in April 2012, gives this example:
<link rel="canonical" href="http://www.example.com/page.php?item=purse">
The specification uses this target for duplicate purse pages whose addresses contain additional category or session parameters. The address is an example from the specification.
Google's implementation guidance places the element inside the HTML <head> and recommends a full URL, including the protocol and hostname. For non-HTML documents such as PDFs, the same guidance supports a canonical declaration through an HTTP response header.
What changes when Google selects a canonical?
Canonicalization is the process of selecting a representative address for duplicate content. Google's explanation of that process lists mobile and desktop versions, HTTP and HTTPS versions, and sorting or filtering pages as possible sources of duplicates. Google groups pages whose main content is identical or very similar, then selects a representative. It crawls the canonical more frequently than the duplicates and uses it as the principal source for assessing content and quality.
Google's canonical URL guidance explains that selecting a canonical can consolidate signals, including links, associated with duplicate addresses. It recommends consistency between declarations and sitemaps, and internal links that point to the preferred address.
For AI search, Google's AI features documentation requires a page to be indexed and eligible for a search snippet before it can appear as a supporting link in AI Overviews or AI Mode. Canonicalization therefore matters when checking which version Google indexes.
How can the selected URL be checked?
In Search Console, Google's URL Inspection tool provides separate fields for the website's declared address and Google's selection. In the indexed result, User-declared canonical reports an explicit declaration. Google-selected canonical, under Page indexing, reports the representative Google chooses.
Comparing these fields reveals whether the declared preference matches Google's selection. The indexed report is the relevant record for this comparison; a live test examines the current page and cannot predict canonical selection.
Related terms
FAQ
Does setting a canonical force Google to use that URL?
Google's canonicalization documentation describes the declaration as a preference. Google can choose another representative after evaluating the pages and their signals.
Can you use robots.txt to choose a canonical?
Google's implementation guidance advises against this. A URL blocked by robots.txt can still enter Google's index without its content.
Can you check the canonical with a live URL test?
Google's URL Inspection help directs you to the indexed data for the selected canonical. The live test cannot predict that selection.
Sources
- Google Search Central, "What is canonicalization", 20 August 2026
- Google Search Central, 'How to specify a canonical URL with rel="canonical" and other methods', 10 July 2026
- IETF, "RFC 6596: The Canonical Link Relation", April 2012
- Google Search Console Help, "URL Inspection tool", accessed 17 October 2026
- Google Search Central, "AI features and your website", 10 December 2025
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