Free SEO tool
Check any page for canonical tag errors in seconds. The checker reads the canonical in the HTML and HTTP headers, then visits the canonical URL to verify that it loads, is indexable and points to itself.
Working on a multilingual site? Test your hreflang with the free hreflang checker
Technical SEO
This tool checks one page. Canonical problems usually come from templates, CMS or plugin settings, filters and parameters, which means they affect hundreds of pages at once. In a technical SEO audit I check canonicals, indexability, redirects and duplicate content across your whole site, and give your developers a prioritised fix list.
Whether the page declares a preferred URL at all, in the HTML or the HTTP Link header.
Two different canonicals (often CMS plus SEO plugin) make Google ignore both.
Canonicals in the <body> are ignored. We read the whole page to find misplaced tags.
Empty tags, invalid or relative URLs, #fragments and http on an https site.
Whether the canonical points to this page, a near-identical variant (slash, www, case) or another page or domain.
The canonical URL must return 200 directly, without redirects or errors.
Whether the target canonicalises to yet another URL, or back to this page.
Conflicts between canonical and noindex, and an og:url that differs from the canonical.
The single-URL check covers one page and its canonical URL. Sitemap mode checks up to 500 URLs from your sitemap. How Google actually picked the canonical (see Search Console) and larger sites are covered in a full audit.
Related guide
How to Do International SEO in 2026: A Step-by-Step Guide
Canonicals and hreflang have to work together on international sites. Learn how to avoid canonical conflicts across language versions.
A canonical tag (<link rel="canonical" href="…">) tells search engines which URL is the preferred version of a page when the same or very similar content is available on several URLs, for example with tracking parameters, filters or http and https versions.
It is best practice to give every indexable page a self-referencing canonical with the absolute URL. It protects the page against duplicate variants created by parameters, sorting, tracking codes and inconsistent internal links.
No. A canonical is a strong hint, not a command. Google can choose a different canonical if other signals, such as internal links, redirects, sitemaps or hreflang, point elsewhere. That is why consistent signals matter.
Common causes are conflicting canonicals, a canonical that redirects or returns an error, very different content between the pages, or internal links and sitemaps pointing to another URL. Search Console's URL Inspection shows which canonical Google selected.
Not with a canonical to another page: noindex says "drop this page" and the canonical says "index that one instead", and Google advises against mixing the two. A noindexed page with a self-referencing canonical is fine.
Yes. Switch to Whole sitemap and enter your sitemap URL, your domain, or upload the sitemap file. The checker reads up to 500 URLs (sitemap indexes and .gz files included) and flags sitemap URLs that redirect, return errors, are noindexed or canonicalise to another URL, plus every canonical error on those pages.