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Canonical Tag Checker

Find out which URL a page tells search engines to index. Read its canonical tag and Link header, follow its redirects, and confirm that every http, https, www and non-www version of the address settles on one URL.

DUPLICATE URL CONTROL

Check a page's canonical URL

Live test
Enter any public page. Query strings are kept, so you can test a URL with tracking parameters to see where its canonical points.

The check runs on the VPSLake server. It fetches the page and up to five related addresses, then discards them. The URL is not saved, and private or internal network addresses are refused.

HOW TO USE IT

Audit a canonical in four steps

Useful after a migration, an HTTPS switch, a CMS change or whenever Search Console reports an unexpected canonical.

  1. 1

    Enter the page URL

    Paste the address exactly as people or campaigns link to it, including any parameters such as ?utm_source=.

  2. 2

    Run the check

    Select Check Canonical. The server follows the redirects, reads the HTML <link rel="canonical"> tags and any canonical in the HTTP Link header.

  3. 3

    Read the findings

    Each finding is marked as passing, a warning or a problem: missing or duplicate tags, tags in the body, relative URLs, http canonicals on HTTPS pages, canonicals that redirect or fail, and noindex conflicts.

  4. 4

    Check the version table

    The four host and protocol versions should end at the same URL. If they do not, add 301 redirects in your web server or CDN so only one version answers.

What a canonical tag does

The same content is often reachable at several addresses: with and without www, over http and https, with tracking parameters, with a trailing slash or a sort order. The canonical tag names the one address you want indexed, so ranking signals are not split across copies.

Search engines treat it as a strong hint. They may override it when it points to a redirect, an error page, a noindex page or content that looks different.

Redirects do the heavy lifting

A canonical tag only helps once a crawler has loaded the page. Redirects stop duplicate versions from loading at all. Force one scheme and one host at the server, then let the canonical handle parameters and near-duplicates.

On Nginx that is a small server block that returns 301 https://example.com$request_uri for the other names; on Apache, a RewriteRule in the virtual host or .htaccess. Behind a CDN, a redirect rule there works too.

The HTTP Link header canonical

Files with no HTML head, such as PDFs, can declare a canonical in a response header: Link: <https://example.com/guide>; rel="canonical". The checker reads the header and the HTML tag, and flags a conflict when they disagree.

If your application or a plugin sends both, make sure they come from the same setting.

A healthy canonical setup

  • One absolute https:// canonical per page, inside <head>
  • Indexable pages point to themselves
  • The canonical URL answers 200 OK without redirecting
  • Internal links, sitemap and canonical all use the same URL form
  • No noindex on a page that should rank

What this check cannot see

The checker reads the HTML your server sends. A canonical that is added or changed later by JavaScript may be missed here, though Google does render pages. It also cannot tell which canonical Google finally selected; use the URL Inspection tool in Search Console for that. Variant tests run once from one VPSLake location, so DNS or CDN rules that differ by region are not covered.

FREQUENTLY ASKED QUESTIONS

Canonical Tag Checker FAQ

It is good practice. A canonical pointing at the page's own clean URL protects it when copies appear through tracking parameters, session IDs, print views or scrapers. Most CMS SEO plugins add one automatically; on a custom application, output it in the shared page template.
Google only honours canonical tags inside <head>. When an element that belongs in the body, such as a stray <div>, an image or a script that writes markup, appears earlier in the head, browsers and parsers close the head there and every tag after it lands in the body. Move the canonical near the top of the head.
It is valid, but risky. A relative path is resolved against whatever host and scheme served the page, so a staging copy or an http version can end up declaring itself canonical. An absolute https:// URL removes that ambiguity.
To a search engine those are four different addresses. If two of them load the page without redirecting, the whole site exists twice. For a subdomain such as blog.example.com, only http and https are tested, because www does not apply.
Yes. Cross-domain canonicals are used for syndicated articles and for sites that publish the same catalogue on two domains. The checker notes it so you can confirm it is intentional; an accidental cross-domain canonical can remove a page from search results.
No. The address is sent in the request body, used for the live fetches and dropped when the answer is returned. Only an anonymous, short-lived rate-limit counter is kept so the tool cannot be abused.