Canonical URL Checker
Check a page's rel="canonical" tag and HTTP Link header, compare it with the final URL and spot missing, multiple or conflicting canonicals and noindex.
https:// is added when no scheme is given.
What is Canonical URL Checker?
This tool fetches a page, follows its redirects and reports the canonical URL declared in the HTML <link rel="canonical"> and in the HTTP Link header. It compares the canonical with the final URL and flags common problems: no canonical, several different canonicals, a different protocol or host, a non-200 page and canonical combined with noindex.
How to use Canonical URL Checker
- Enter the page URL.
- Press Check.
- Review the table: final URL, status code, canonical from HTML, canonical from the Link header, robots directives and hreflang links.
- Read the findings list for warnings and what they mean.
When to use Canonical URL Checker
Use it to audit duplicate-content setups, paginated or filtered URLs and migrations. The page is fetched without JavaScript, so canonical tags inserted by client-side scripts are not seen; Google may also choose a different canonical than the one you declare.
How Canonical URL Checker works
The page is fetched by AlgoKit's SSRF-guarded Pages Function (up to 10 redirects, 8 s timeout, at most 512 KB of HTML). The HTML is scanned for <link> and <meta> tags after removing comments and scripts; canonical hrefs are resolved against the page URL (respecting <base>). Link headers and X-Robots-Tag are read from the final response. The comparison and findings are computed in your browser.
Common Use Cases
- Check that product variants point their canonical to the main product URL.
- Verify that each page has a self-referencing canonical after a CMS change.
- Detect templates that output two conflicting canonical tags.
- Spot pages that are noindex and canonicalized at the same time.
FAQs
Should every page have a canonical tag?
It is recommended. A self-referencing canonical makes it clear which URL to index when tracking parameters or alternate paths produce duplicates.
Is the canonical a directive?
No, search engines treat it as a strong hint. Redirects, internal links and sitemaps should point to the same URL to make it effective.
Why is a canonical on a 404 page useless?
Search engines only consider canonical tags on pages that return 200; error pages are dropped regardless.