Free Canonical Tag Checker — Find Canonical Errors in Your Page Source
Paste a page's URL and its HTML source and this free canonical tag checker finds the canonical link, flags missing, duplicate, relative or misplaced tags, and compares it with the page URL. No signup, nothing leaves your browser.
Paste the page URL and its HTML source to check the canonical tag.
What the Checker Looks For
- Missing canonical. No
rel="canonical"link was found. Google can still pick a canonical on its own, but a tag states your preference. - More than one canonical. Several tags, especially pointing at different URLs, give conflicting signals and may be ignored.
- Canonical outside the head. The tag belongs inside
<head>. One that lands in the body is not a valid placement. - Empty, relative or odd URLs. An empty href, a relative path, a fragment (
#) or a non-http scheme is flagged. - Canonical versus page URL. The tool compares protocol, host, path and query, so you can see whether the page points to itself or somewhere else.
- Mixed signals. A canonical alongside a
noindexrobots meta tag, or a different canonical in the HTTP header, is called out.
How to Get the Page Source
Open the page in your browser, press Ctrl+U (or Cmd+Option+U on Mac) to open the source, select everything and paste it into the box above. Use the raw source rather than the Elements panel when you can, because it shows what the server sent before any JavaScript changed it. If the canonical is added by JavaScript, check it in the URL Inspection tool in Search Console as well.
This tool reads only what you paste. It does not fetch the page, so it cannot see redirects, the rendered page or what Google actually chose as the canonical. A canonical is a hint, not a command, and Google may select a different URL.
Canonical Tag Checker FAQs
Why do I need to paste the source instead of entering a URL?
Browsers block a page from reading another site's HTML, and fetching it through a server would mean sending your data to us. Pasting keeps everything in your browser.
Should every page have a self-referencing canonical?
It is a common and safe practice, because it states the preferred URL when the same page can be reached with tracking parameters or different casing. It is not required.
Is a relative canonical URL wrong?
Relative paths can work, but an absolute URL leaves less room for error, so the tool recommends the absolute form.
What if the canonical points to a different page?
That is valid when the page is a duplicate or near-duplicate of the target. The tool lists the differences so you can confirm it is intentional and not a copied template.
Does this tool store or send my data anywhere?
No. The source is parsed in your browser with JavaScript — nothing is uploaded, logged, or stored on any server, including ours.
Want a full technical audit of your site?
Contomatix checks canonicals, indexing and crawl issues across every page that matters.