Canonical URL Definition
A canonical URL is the representative URL for duplicate or very similar pages. Canonicalization identifies that representative. In other words, the concept connects a group of pages with one URL that represents them. The starting point is the relationship between those pages: they are duplicates, or their content is very similar.
This definition includes both duplicate pages and very similar pages. Canonicalization therefore concerns more than exact copies. When you encounter the term, read “representative URL” as the URL identified to stand for those pages. That meaning provides the foundation for understanding a canonical link and the preference it communicates.
A rel="canonical" link is a strong signal for the preferred URL. According to Google Search Central, that signal communicates which URL is preferred as the representative. The word “preferred” matters here: it describes a choice being communicated. It does not mean that the preferred version is guaranteed to be the version shown in Search.
Google ultimately determines which version to show in Search. This is the key distinction between expressing a preference and making the final selection. A canonical link can communicate the preferred URL strongly, while Google still makes the decision. The expressed preference and Google’s final selection are separate parts of the explanation.
Imagine a group of very similar pages. One URL is indicated as preferred through a rel="canonical" link. That link gives Google a strong signal about the preferred representative, while Google still determines the version it will show in Search. The preference and the outcome should therefore be described separately.
The terminology is easier to follow when each term has a clear role. Canonicalization names the identification of a representative URL. Canonical URL names that representative. A rel="canonical" link provides a strong preference signal. Keeping those roles distinct helps explain the concept without treating a stated preference as a confirmed decision by Google.
When discussing a specific URL, be clear about which part of canonicalization you mean. You might be describing the URL expressed as preferred through a canonical link, or the version Google ultimately chooses to show in Search. Using precise language preserves the central distinction in Google Search Central’s explanation: a strong preference signal accompanies Google’s final choice.
Source and attribution: This explanation is adapted in English from Google Search Central’s documentation on canonicalization, using the supplied Simplified Chinese source. Credit: Google Search Central. The source material is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). The wording above is an English paraphrase.