Canonical tag
A canonical tag signals the preferred URL for duplicate or very similar content. Search engines consider it alongside other signals when choosing a canonical.
Duplicate URLs are common: tracking parameters, print versions, and http vs https all create copies. Without a canonical, engines pick one for you, and often the wrong one.
Unique preferred pages usually use self-referencing canonicals. Incorrect cross-page canonicals can confuse that preference; the declared canonical and Google's selected canonical need not match.
A practical example
A product URL with a tracking parameter points its canonical to the clean product URL.
A common mistake
Pointing every page to the homepage, or treating a canonical as a guaranteed instruction.
How to check it
Inspect the canonical in server HTML, check that its destination is suitable, and compare Google's selected canonical where access is available.
Related terms
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