Free Canonical Tag Checker: audit any URL's rel=canonical
Paste a URL and we read its canonical from both the HTML head and the HTTP Link header — then tell you if it's self-referencing, missing, cross-domain, or pointing to a redirect, plus exactly what to fix. No sign-up.
Free, no sign-up. We read the page's rel=canonical from its HTML and HTTP headers, then tell you if it's self-referencing, cross-domain or missing.
What a canonical tag is & why it matters
A canonical tag (rel="canonical") is a single line in a page's HTML head that names the master version of that content. When the same page is reachable from several URLs — with tracking parameters, trailing slashes, uppercase variants, or print and AMP versions — the canonical tells Google which URL to index and rank, and consolidates link signals onto it instead of splitting them.
Get it wrong and you can quietly deindex pages, waste crawl budget on duplicates, or dilute the authority of your most important URLs. That's why a quick canonical check belongs in every publishing and migration checklist. For a deeper walkthrough, read our guide to canonical tags.
What the canonical checker validates
- rel=canonical in the HTML <head>
- rel=canonical in the HTTP Link header
- Self-referencing vs. cross-page canonicals
- Cross-domain canonicals
- Canonicals pointing to a 3xx redirect or a 4xx page
- Multiple or conflicting canonical tags on the same URL
- Canonical mismatch with the final URL after redirects
- Conflicts with hreflang, og:url and noindex signals
How to read your result
Self-referencing
The page points to its own URL. This is the correct, recommended setup for any standalone, indexable page — it removes ambiguity and is exactly what you want to see.
Points elsewhere / cross-domain
The canonical points to a different URL — another page on your site, or a different domain. Right for duplicates and syndicated content, but a red flag if this page should rank on its own.
Missing
No canonical found in the HTML or headers. Google will choose one for you. Add a self-referencing canonical to take back control, especially on parameterized or duplicate pages.
Common canonical mistakes — and how to fix them
Canonical to a redirected or 404 URL: the canonical points at a URL that redirects or no longer exists, so the signal is wasted.
Fix: always canonicalize to a live, 200-status final URL.
Multiple canonical tags: two or more rel=canonical tags on one page conflict, and Google may ignore all of them.
Fix: keep exactly one canonical tag per page.
Accidental cross-domain canonical: a template or migration leaves the canonical pointing at a staging or old domain.
Fix: point the canonical to the correct production URL on this domain.
Canonical fights other signals: the canonical says "index this" while a noindex tag, robots block or redirect says otherwise.
Fix: align canonical, robots, sitemap and internal links on one URL.
Find canonical issues across your whole site
A one-off check is great for a single page. SEOcrawl AI surfaces canonical and indexation issues straight from Google Search Console at scale — like "Alternate page with proper canonical tag" — so you can tag them via rules, manually or over MCP, and tie every issue to your rankings and traffic. See it all in one place instead of page by page.
FAQs
What is a canonical tag?
A canonical tag (rel="canonical") is one line in the HTML head that names the master version of a page. When the same or very similar content appears on multiple URLs, the canonical tag tells search engines which one to index and rank, and consolidates link signals behind it rather than splitting them between duplicates.
What's an example of a canonical tag?
It looks like this in the page source: <link rel="canonical" href="https://example.com/blue-sneakers" />. That line tells Google /blue-sneakers is the master URL, even if the product is also reachable at /blue-sneakers?utm_source=email or /blue-sneakers/size-42. Every indexable page should have one, ideally pointing to itself.
When should I use a canonical tag?
On every indexable page, by default, pointing to itself. You need one specifically when the same content is reachable from multiple URLs: tracking parameters, filter or sort variants, print or AMP versions, syndicated copies. If the page should rank standalone, the canonical points to its own URL. If it's a duplicate, it points to the master.
How do I check a page's canonical?
Paste the URL into the tool above and click "Check canonical". We fetch the page, read rel=canonical from both the HTML head and the HTTP Link header, and tell you whether it's self-referencing, points elsewhere, is cross-domain, missing or conflicting. You can also view the source and search for "canonical" manually, but the tool catches duplicate tags and post-redirect mismatches.
What is a self-referencing canonical?
A self-referencing canonical is when a page's canonical tag points to its own URL. It's the recommended default for any standalone indexable page: it removes ambiguity from tracking parameters, trailing slashes and uppercase variants, and tells search engines explicitly which URL is the one to index.
How do I fix a canonical tag?
If it points to a redirect or 404, change it to the final 200 URL. If there are multiple canonical tags, keep only one. If it points to staging or another domain by mistake, switch it to production. If it fights a noindex or robots rule, pick one signal and align the rest. Re-check the page after the fix to confirm.
What's the difference between canonical, noindex and a 301 redirect?
A canonical says "this is the master version, consolidate signals to it" and both URLs stay live. A noindex says "don't show this in search" and the URL stays accessible. A 301 redirect says "this URL is gone, send the user and the link equity to a new one." Use canonical for duplicates, noindex for thin content, 301 for removed or moved pages.
How is this tool different from Google Search Console's canonical report?
GSC's Page Indexing report tells you which canonical Google chose for each URL, sometimes a different one than you declared. This checker reads the canonical you actually set in your HTML and HTTP headers. Use both: GSC for Google's verdict on what got indexed, this tool to verify what you're sending in the first place.