What Is a Canonical URL and How to Fix Duplicate Content
Guide · SEO Tools
Duplicate content happens more often than people expect — the same product page reachable through two different URL paths, a page available both with and without a trailing slash, or content syndicated across multiple sites. A canonical tag tells search engines which single version is the "real" one to index and rank.
What causes accidental duplicate content
- The same page accessible at both
https://example.com/pageandhttps://www.example.com/page - URL parameters that don't change the actual content — tracking codes, sort orders, session IDs
- HTTP and HTTPS versions of the same page both being reachable
- The exact same article published on your own site and syndicated to another platform
None of these are usually intentional — they're just side effects of how a site or CMS is set up — but search engines still have to decide which version to show, and a canonical tag is how you tell them explicitly instead of leaving it to guesswork.
The tag itself
<link rel="canonical" href="https://example.com/the-real-page">
Place this in the <head> of every version of the page, all pointing to the same single canonical URL — including on the canonical page itself, pointing to its own URL. That last part matters: a page should always self-reference its own canonical tag, not just the duplicate versions.
Generating and checking yours
- Enter your page's real, preferred URL into the Canonical URL Generator to get the exact tag to paste into your page's head.
- Make sure every duplicate or near-duplicate version of a page points to the same canonical URL, consistently.
- Confirm with a "view page source" check that the tag actually made it into the live HTML, not just your template file.