Free tool
Canonical Tag Scanner
Read the canonical on every page and catch the ones pointing somewhere they should not.
How it works
What is the Canonical Tag Scanner?
The Canonical Tag Scanner is a free tool that reads the canonical tag on a page and on up to 20 more URLs from the site's sitemap. It reports whether each canonical points to the page itself, to another URL, to another domain, or is missing or duplicated, alongside each page's HTTP status code.
How to use the Canonical Tag Scanner
- Paste the URL of the page to check. The path matters: that page gets the main verdict.
- Press Scan tags. The tool also reads the sitemap at /sitemap.xml and scans up to 20 of the URLs it lists.
- Read the verdict for your page: the canonical it found, the HTTP status code and the content type, with an analysis and a recommendation.
- Check the site-wide score, duplicate content risk and crawl efficiency, then the Scanned Pages table, where each row is marked SELF, OTHER, OFF-ORIGIN, MISSING or MULTIPLE.
What is a canonical tag used for?
A canonical tag tells search engines which URL, out of several that show the same content, should be indexed. It is written as <link rel="canonical" href="..."> in the page's head or sent as a Link HTTP header, and this scanner reads both.
The same page is often reachable at several addresses: with and without a trailing slash, with tracking parameters, on http and https. The canonical folds them into one. It is a hint, not a directive: Google weighs it against redirects, internal links and sitemaps, and can choose a different URL. To see whether Google kept the page at all, use the Google Index Checker.
What happens when a canonical tag points to another domain?
Google treats the other domain's URL as the version to index, and your page can drop out of results. That is right for syndicated content and damaging when it happens by accident, for example when a staging domain is hard-coded in a template or a theme ships with its vendor's URL.
The scanner marks these rows OFF-ORIGIN so they stand out from canonicals to another page on your own site. The page keeps loading normally, so nothing else will warn you.
Missing, multiple or relative canonical tags: what should I fix first?
Fix multiple canonical tags first. When a page carries more than one, Google may ignore all of them and choose its own canonical. This usually happens when a plugin and a theme each add one, and the scanner flags any page with two or more, even when they agree.
A missing canonical is a warning, not a failure: Google picks one itself, and on a simple site it often picks right. A relative href works because it resolves against the page URL, but an absolute URL is safer. The table shows whether a problem is one page or the whole template.
What is a canonical error in SEO?
A canonical error is a canonical tag that sends search engines somewhere they cannot use, or that contradicts the page's other signals. The usual cases are a canonical pointing at a URL that redirects, returns a 404 or carries a noindex tag, every page of a paginated series pointing at page one, and http canonicals left on a site that now runs on https.
The scanner reports the HTTP status code of each page it reads, so a canonical sitting on a broken page shows up instead of passing as healthy. It does not fetch the canonical target itself. For any row marked OTHER, open the target and confirm it loads with a 200 and is allowed into the index; the Noindex Checker tests the second part.
Questions
- What is a canonical tag in SEO?
- A canonical tag in SEO is a
<link rel="canonical">element that names the preferred URL for a page's content. Search engines use it to choose which of several duplicate URLs to index and to combine their signals on that one. - Should every page have a self-referencing canonical tag?
- Yes, for a normal indexable page a self-referencing canonical tag is the safe default. It stops tracking parameters and trailing-slash variants from competing with the clean URL. Only real duplicates, such as a filtered or print view, should point elsewhere.
- What is the difference between a canonical tag and a 301 redirect?
- A 301 redirect sends visitors and crawlers to another URL, while a canonical tag leaves both on the page and only tells search engines which URL to index. Use a redirect when the old URL should stop working, and a canonical when both URLs need to stay live.
- How do I add a canonical tag in HTML?
- Add
<link rel="canonical" href="https://example.com/page">inside the page's<head>, using the full absolute URL of the preferred version. Most CMSs and SEO plugins set one for you, so check you are not adding a second. - Are canonical tags important for SEO?
- Canonical tags matter most where the same content lives at several URLs, such as shops with filters or sites that add tracking parameters. On a small site with clean URLs Google usually picks the right page without one, but a self-referencing canonical costs nothing. The SEO Friendly URL Checker flags query parameters in any URL you test.
- Which pages does the canonical scanner check besides mine?
- The scanner reads
/sitemap.xmlat the root of your domain and checks up to 20 of the URLs it lists. If that file is a sitemap index, it opens only the first child sitemap. Responses that are not HTML, such as PDFs, and pages that do not answer within a few seconds are left out of the table.
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