Canonical Tag Checker
Paste a page’s HTML to inspect its canonical tag: whether it exists, is self-referencing, uses an absolute URL, and matches the og:url. Common mistakes are flagged. Everything runs in your browser.
Page HTML
About the Canonical Tag Checker
The Canonical Tag Checker inspects pasted HTML and finds the rel=canonical link in the page head, then reports the canonical URL it points to. A canonical tag tells search engines which URL is the preferred version of a page, which helps avoid duplicate content problems. This tool does not fetch a URL. You paste the page source yourself and it parses it locally. Everything runs in your browser, so nothing you paste is sent to a server.
How it works
- Open the live page you want to check in your browser.
- View the page source with Ctrl+U on Windows or Cmd+Option+U on Mac, then select all and copy the HTML.
- Paste the HTML into the input box on this page.
- Read the detected canonical URL the tool reports, and confirm it matches the URL you expect.
Features
- Finds the rel=canonical link element in pasted HTML and shows the canonical URL it references.
- Tells you when no canonical tag is present so you can spot pages that are missing one.
- Flags whether the canonical is self-referencing or points to a different URL.
- Parses the HTML you paste, with no URL fetching, so it works on staging sites, password-protected pages, and local files too.
- Fully client-side. No accounts, no uploads, nothing sent to a server.
Frequently asked questions
What does a rel=canonical tag do?
It sits in the page head and tells search engines which URL is the preferred, canonical version of a page. When the same or very similar content is reachable through multiple URLs, the canonical tag points engines to the one version that should be indexed and that ranking signals should consolidate to.
What is a self-referencing canonical?
It is a canonical tag whose URL is the same as the page it appears on. This is a common best practice. It confirms to search engines that the current URL is the preferred one and helps prevent duplicate versions, such as ones with tracking parameters, from being treated as separate pages.
What happens if the canonical points to the wrong page or another domain?
Search engines may drop the current page from the index and credit the URL in the canonical instead. A wrong or cross-domain canonical can therefore deindex content or hand ranking signals to a page you did not intend. Checking the reported URL helps you catch these mistakes before they cost you traffic.
Do http vs https or trailing-slash differences matter?
Yes. A canonical that uses http when your site serves https, or that adds or drops a trailing slash compared to the real URL, is treated as a different URL. These mismatches can split signals or point engines at a version that redirects, so compare the reported canonical carefully against the live URL.
Why do I have to paste HTML instead of entering a URL?
Browser security, specifically CORS, blocks client-side code from reading the raw HTML of other sites, and this tool never fetches user URLs from a server. Pasting the source keeps everything in your browser, and it also lets you check pages a fetcher could not reach, such as staging, password-protected, or local files.