Canonical URLs: Solving Duplicate Content Issues

Duplicate content occurs when the same or very similar content is accessible at multiple URLs. This dilutes your SEO value and confuses search engines about which version to index.

Common Causes of Duplicate Content

URL parameters like tracking codes and session IDs create duplicate URLs. HTTP and HTTPS versions of the same page are seen as duplicates. WWW and non-WWW versions are separate URLs. Trailing slashes create different URLs. Print-friendly page versions duplicate content.

How Canonical Tags Work

The canonical tag tells search engines which URL is the preferred version. All duplicate pages should include a canonical tag pointing to the original. Search engines consolidate ranking signals to the canonical URL.

Self-Referencing Canonicals

Every page should include a canonical tag pointing to itself. This prevents issues when parameters are appended to the URL and reinforces the preferred URL format.

Implementation Tips

Use absolute URLs in canonical tags, not relative. Ensure the canonical URL is accessible and returns a 200 status code. Do not canonicalize paginated content to page one. Use our Canonical URL Builder to generate correct tags.

Canonical vs Redirect

Use canonical tags when you want both URLs to remain accessible. Use 301 redirects when you want to permanently move traffic from one URL to another. Redirects are stronger signals than canonical tags.