Canonicalization
Canonicalization tells search engines which URL is the authoritative version of a page when duplicates or near-duplicates exist, consolidating ranking signals onto one URL.
Canonicalization is how you tell search engines which URL is the authoritative version of a page when several URLs serve the same or similar content. Done right, it consolidates ranking signals — links, relevance, authority — onto one URL instead of splitting them across duplicates.
Why it matters
Large sites generate duplicates constantly: tracking parameters, faceted-navigation combinations, HTTP and HTTPS versions, www and non-www, print views, session IDs. Without a clear canonical signal, Google picks one itself — and it may not pick the one you want, or it may split equity across several, weakening all of them.
You declare a canonical with a rel="canonical" link element, and reinforce it with consistent internal linking, 301 redirects, and sitemap entries. The declared canonical is a strong hint, not a command; the URL Inspection tool shows the difference between your user-declared canonical and Google’s selected canonical.
Example
A product reachable at /shoes/air-jordan-1, /shoes/air-jordan-1?color=red, and /shoes/air-jordan-1?utm_source=email is one page with three URLs. Point all three canonicals at /shoes/air-jordan-1, and the links and authority earned by any variant flow to that single URL, which competes far better than three fragments would.
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