Canonical URL
A canonical URL is the preferred version of a page that search engines should treat as the main URL when similar or duplicate content exists across multiple URLs.
Key takeaways
- A canonical URL tells search engines which version of a page to index when duplicates exist.
- It consolidates ranking signals like links and authority to the preferred URL.
- Implement via
<link rel="canonical">in the HTML head of all duplicate pages. - Google may override your canonical if its signals indicate a different URL is more representative.
- Use canonicals for tracking parameters, faceted navigation, and protocol/domain variants.
Canonicalization is a core SEO control for managing duplicate content across your site.
Example
Imagine you sell shoes. The same product page is accessible at:
https://example.com/shoes/red-sneakershttps://example.com/shoes/red-sneakers?color=redhttps://example.com/shoes/red-sneakers?utm_source=facebook
By setting the canonical URL to https://example.com/shoes/red-sneakers, you tell Google to treat that as the main version and consolidate ranking signals (links, authority) to it.
When should I use this?
Use a canonical URL when:
- You have duplicate or near-duplicate pages (e.g., printer-friendly versions, session IDs).
- You use faceted navigation (filters, sorting) that creates many URL variants.
- You have tracking parameters (UTM, referral) that don't change content.
- You serve the same content on HTTP and HTTPS, or www and non-www.
- You syndicate content to other sites and want to point back to the original.
What it is not
- A substitute for a 301 redirect when the duplicate page should not remain accessible.
- A way to hide content from users (users can still access the non-canonical URL).
- A guarantee that Google will always use your declared canonical.
- A replacement for noindex if you want to exclude a page from indexing entirely.
Quick start
- Identify the preferred URL for a set of duplicate pages.
- Add
<link rel="canonical" href="https://example.com/preferred-url/" />in the<head>of all duplicate pages. - Ensure the canonical URL is accessible (returns 200) and not blocked by robots.txt.
- Use absolute URLs (including
https://and domain) to avoid confusion. - Verify implementation using Google Search Console's URL Inspection tool.
Common mistakes
- Using canonicals as a substitute for redirects when the duplicate page should not remain accessible.
- Pointing canonicals inconsistently across a chain of pages instead of directly to the final preferred URL.
- Canonicalizing pages that are not truly duplicates or near-duplicates, which can confuse search engines.
- Assuming Google will always obey the declared canonical even when other signals conflict.
Next step
FAQ
What is a canonical URL in SEO?
A canonical URL is the preferred version of a page that search engines should treat as the main URL when similar or duplicate content exists across multiple URLs.
How do I add a canonical tag in HTML?
Add <link rel="canonical" href="https://example.com/preferred-url/" /> in the <head> section of the page.
What is the difference between a canonical URL and a 301 redirect?
A canonical URL tells search engines which version to index while keeping both URLs accessible; a 301 redirect sends users and search engines to a different URL entirely.
Can Google ignore my canonical tag?
Yes, Google may choose a different canonical if its signals indicate another URL is more representative of the content.
Related topics
Sources
- Google Search Central — Primary source for how Google defines canonicalization and canonical URLs.
- Google Search Console Help — Explains canonical URLs, duplicate groups, and how Google selects canonicals.
- Conductor Academy — Clear SEO-focused explanation of rel=canonical and duplicate-content use cases.
- Moz Learn SEO — Well-known SEO reference covering canonical tags and practical implementation.
Reviewed by Lucía Marín, Founding editor.