Canonical URL Checker

A canonical URL is the preferred version of a webpage when multiple URLs serve the same or very similar content. Declaring a canonical URL tells search engines which version to index and assign ranking signals to. Without a canonical, search engines must choose for themselves, which can result in the wrong URL being indexed or ranking signals being split across duplicates.

The tool makes an HTTP request to the URL you enter and inspects two locations: the HTTP response headers (looking for a Link: ; rel="canonical" header) and the HTML source (looking for a element in the ). Results from both sources are displayed and compared. If both are present and agree, that is shown. If they conflict or one is missing, that is flagged.

Both methods declare the same thing — the preferred URL — but through different channels. The HTML canonical tag is placed inside the section of the page HTML. The HTTP header canonical is sent as part of the server's HTTP response before the HTML is delivered. The HTML tag method is more common and universally supported. The HTTP header method is useful for non-HTML resources like PDFs, where there is no HTML to modify. If you are using a CMS, the HTML tag is the correct approach.

If no canonical tag is present, search engines will attempt to identify the preferred version on their own. This is generally fine for straightforward sites, but it creates risk when the same content is accessible at multiple URLs — for example, /page and /page/, or http:// and https://. In those cases, Google may index the wrong variant and distribute link equity across multiple URLs instead of consolidating it. Adding a self-referencing canonical removes the ambiguity.

A self-referencing canonical is when the canonical tag on a page points back to the page itself. For example, if you check https://example.com/blog/post/ and the canonical is https://example.com/blog/post/, that is self-referencing. This is the correct and expected state for any page you want indexed. It confirms: "This URL is the authoritative version of this content."

Conflicting canonical signals occur when the HTTP header canonical and the HTML canonical tag point to different URLs. This usually happens when a CMS or SEO plugin sets the HTML canonical while the server or CDN is also setting an HTTP header canonical independently. To fix it: first, identify which source is setting each canonical (check server config, CDN settings, and CMS/plugin settings). Then either align both to the same URL, or disable one of them — typically the HTTP header — to leave a single, unambiguous canonical signal.

Yes, this is one of the canonical tag's primary use cases. If you have multiple pages with substantially similar content — such as product pages with minor variations, or the same article syndicated in multiple categories — you can add a canonical on each duplicate pointing to the original preferred URL. Search engines will treat the duplicates as secondary and focus indexing and ranking signals on the canonical URL. Note that this is a hint rather than a directive; search engines may not always follow it, but it is the standard recommended approach.

The tool works on any publicly accessible URL. It does not require login credentials or authentication. Pages behind a login, paywalls, or IP-restricted environments will not return a canonical result since the tool cannot fetch the page content. For those cases, you would need to inspect the canonical manually by viewing the page source directly in a browser.