A canonical tag (rel="canonical") is an HTML element that tells search engines which version of a page is the preferred, authoritative copy when multiple URLs serve similar or identical content. It prevents duplicate content issues by consolidating ranking signals to one URL.
Why Canonical Tag matters for SEO
Without canonical tags, search engines may index multiple versions of the same page (with/without trailing slashes, HTTP vs HTTPS, parameter variations), splitting your ranking signals and causing keyword cannibalization. Every indexable page should have a self-referencing canonical tag.
Pro tip on Canonical Tag
Add a self-referencing canonical tag to every page. Ensure the canonical URL matches the exact page URL (same protocol, same trailing slash). Never set canonical to a 404 page. Don't use canonical and noindex on the same page (conflicting signals).
Canonical Tag vs 301 Redirect
A canonical tag suggests a preferred URL while keeping both accessible. A 301 redirect permanently moves users and crawlers from one URL to another. Use 301s for permanent URL changes; use canonicals when both URLs need to exist.
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