On-page SEO
Canonical Tag
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What is Canonical Tag?
A canonical tag is an HTML link element (`<link rel="canonical" href="...">`) placed in the `<head>` of a page to indicate the preferred version of a URL when duplicate or near-duplicate content exists. It tells search engines which URL should be indexed and credited with ranking signals, consolidating all authority onto a single canonical URL.
Canonical tags are essential for managing e-commerce product variants, paginated content, URL parameters, and syndicated articles. They can point to the same page (self-referencing canonicals are a best practice) or to a completely different URL on the same or another domain. Unlike a 301 redirect, a canonical tag does not redirect users — it is a hint to search engines only.
Why it matters for SEO
Without canonical tags, search engines may index multiple versions of the same content and split link equity between them, weakening the ranking potential of the intended page. Correct canonicalization ensures ranking signals consolidate on the right URL and prevents index bloat.
Example
A blog post is reachable at https://example.com/blog/seo-tips and at https://example.com/blog/seo-tips?utm_source=newsletter. Both versions include <link rel="canonical" href="https://example.com/blog/seo-tips"> in the head, so Google indexes the clean URL and credits links to either version to that one page. The canonical is a strong hint rather than a command, so internal links and the sitemap should use the clean URL too.
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