Canonical URL

Why It Matters

Duplicate content dilutes ranking signals across multiple URLs, weakening overall performance. Canonical tags consolidate authority to one preferred URL, preventing self-competition and ensuring search engines index the right version. Critical for e-commerce sites, content syndication, and sites with URL parameters.

How It Works

The canonical tag is added to the HTML head section, pointing to the preferred URL version. When search engines encounter multiple pages with similar content, they use the canonical tag to determine which version to index and rank. All ranking signals from duplicate versions are consolidated to the canonical URL.

Use Cases

• An e-commerce product available in multiple colors has separate URLs - all point canonical to the main product page
• A blog post syndicated on Medium includes a canonical tag pointing back to the original on your domain
• HTTP and HTTPS versions of the same page both point canonical to the HTTPS version

Best Practices

• Self-reference canonical tags on all pages to prevent accidental duplication
• Use absolute URLs (full domain) in canonical tags, not relative paths
• Ensure canonical URL is accessible and returns 200 status code, not 404 or redirects
• Don't canonical to a different page with substantially different content
• Check that canonical tags aren't conflicting with redirects or robots.txt blocks
• Use canonical tags consistently with hreflang for international sites