SEO & GEO
What is Canonical Tag?
Definition
An HTML tag that tells search engines which URL is the authoritative version of a page — preventing duplicate content issues when the same content is accessible at multiple URLs.
In more detail
A canonical tag (`<link rel="canonical" href="https://example.com/page/" />`) signals to search engines: consolidate all ranking signals to this URL, not any of the duplicates. Without it, Google has to guess which version to index — and often guesses wrong, splitting your page authority across variants.
Duplicate content arises naturally and constantly: HTTP vs HTTPS, www vs non-www, trailing slashes, UTM parameters creating unique URLs, pagination, printer-friendly versions, and syndicated content. Each variation is technically a unique URL that search engines may index separately.
Best practice is to implement self-referencing canonicals on every page — each page points to itself as the canonical. This makes your intent unambiguous even if a duplicate version is created later, and signals clean architecture to search engines.
Why it matters
Incorrect or missing canonicals dilute your SEO equity. When authority is split across duplicate URLs, none of them rank as well as a single canonical would. This is one of the most common and most impactful technical SEO fixes on established sites.
Further reading
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