Free Canonical Tag Checker
Check the canonical tag of any URL instantly. Detect missing, self-referencing, or incorrect canonicals that cause duplicate content issues and hurt your SEO.
Enter a URL to check
How to Use the Canonical Tag Checker
Enter any URL and click Check Canonical. The tool fetches the page and reads both the HTML <link rel="canonical"> tag and the HTTP Link header.
What Each Result Means
Canonical URL
The URL declared as the canonical version. Should be an absolute, clean URL without query parameters (unless intentional).
Source
Whether the canonical was found in the HTML <head> or the HTTP response header. Both are valid — HTML is more common.
Self-Referencing
Good! The canonical points to the same page, explicitly claiming canonical status and preventing other pages from outranking it.
Issues Detected
Any problems found: missing canonical, relative URL, HTTP canonical on HTTPS page, or canonical pointing to a different domain unexpectedly.
Canonical Tag Best Practices
| Rule | Why It Matters |
|---|---|
| Always use absolute URLs | Relative canonicals can resolve incorrectly on CDNs or subdomains |
| Use HTTPS in canonicals | HTTP canonicals on HTTPS pages signal a conflict to Google |
| Add to every page | Even unique pages benefit from self-referencing canonicals |
| One canonical per page | Multiple conflicting canonicals are ignored by Google |
| Match your sitemap | All URLs in your sitemap should be the canonical version |
Frequently Asked Questions
What is a canonical tag and why does it matter for SEO?
A canonical tag (<link rel="canonical">) tells search engines which version of a page is the 'master' version when duplicate or near-duplicate content exists at multiple URLs. Without it, Google may split your link equity across duplicates or pick the wrong version to index — both hurt rankings.
What does 'self-referencing canonical' mean?
A self-referencing canonical means the canonical tag points to the same URL as the page itself. This is good practice — it explicitly tells Google this page is the canonical version and prevents other pages from accidentally claiming authority over it.
What happens if a page has no canonical tag?
Without a canonical tag, Google will attempt to determine the canonical URL itself. It usually picks correctly, but there's a risk it chooses a URL with query parameters or a duplicate version. Always add explicit canonicals on important pages to be safe.
Can a canonical tag point to a different domain?
Yes — cross-domain canonicals are valid and useful when syndicating content. If your content appears on another site, you can ask them to add a canonical pointing back to your original URL. Google will then credit the link equity to your page.
What is the difference between a canonical in HTML vs HTTP header?
Both methods tell Google the canonical URL. The HTML <link rel="canonical"> is placed in the <head> section and works for all page types. The HTTP Link header is better for non-HTML files like PDFs. Google supports both equally.
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