Canonical URL
A canonical URL is the address a page declares as its true location with rel=canonical. It consolidates duplicates and must match the sitemap and hreflang.
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What a canonical URL is
A canonical URL is the address a page declares as its true location, using a rel="canonical" link in the head. It answers a question a crawler would otherwise have to guess: when several URLs show the same content, which one should appear in the index and carry the signals?
What it does and does not control
The canonical tag consolidates duplicate addresses. It does not guarantee that a search engine will follow the declaration, and it does not make two pages with different content into one. It also does not replace a redirect: for a page that has permanently moved, the redirect is the mechanism, and the canonical on the destination is a separate check.
What a correct one looks like
Absolute, not relative. Self-referencing on pages that should be indexed. Free of query strings that do not change the content. Consistent with the sitemap and the hreflang pairs, because three files that disagree about a page’s address leave a crawler with three candidates. One trailing-slash convention, one host, one protocol.
Where it fits in the product
The SEO work treats the canonical as a gate rather than a suggestion: the migration contract compares canonicals page by page and fails the change set when one points at another document. The glossary entry for the redirect map covers the case where the address itself changes.
Related terms
- Redirect map
A redirect map records the decision for every legacy URL: keep the path, redirect it, remove it or flag it for review. It is tested before cutover.
- SEO contract
An SEO contract is the fixed list of search facts a migration must keep — URLs, titles, canonicals, schema, sitemap and robots — checked as a pass-or-fail gate.
- Core Web Vitals
Core Web Vitals are Google page-experience metrics — Largest Contentful Paint, Interaction to Next Paint, Cumulative Layout Shift — measured on real devices.
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