Canonicalization is the process of choosing a single, preferred URL (called the canonical URL) among multiple URLs that show the same or very similar content.
Google uses this process to avoid showing duplicate content in search results, ensuring users see the best version of a page.
Why Does Duplicate Content Happen? #
- Region variants: Same content for USA vs UK but different URLs
- Device variants: Separate mobile and desktop URLs
- Protocol variants: HTTP vs HTTPS versions of the same page
- Site functions: Sorting or filtering creating multiple URLs for similar content
- Accidental duplicates: Staging or demo pages left open accidentally
Why Is Canonicalization Important? #
- Prevents confusion about which page is the “real” one
- Avoids duplicate listings in search results
- Helps consolidate ranking signals like backlinks to one page
- Makes tracking and analytics more accurate
- Reduces unnecessary crawling of duplicates
How Google Chooses the Canonical URL #
When Google indexes pages, it looks for duplicate or near-duplicate content and picks the URL that seems:
- The most complete and useful for users
- Has signals like HTTPS, redirects, sitemap presence, or canonical tags pointing to it
You can suggest a canonical URL using the rel=”canonical” tag or by setting preferred versions in sitemaps and redirects, but Google treats it as a hint, not a rule — it may pick a different canonical URL based on its own assessment.
Example: #
If your site has:
- http://example.com/page
- https://example.com/page
- https://m.example.com/page (mobile version)
Google might select https://example.com/page as canonical, but show the mobile version in search results to mobile users.
Quick FSIDM Pro Tip: #
Always use canonical tags on duplicate or very similar pages to guide Google’s canonicalization. It improves SEO and avoids dilution of page authority.