Free Canonical Tag Checker: audit any URL's rel=canonical
Paste a URL and we read its canonical tag from both the HTML and the HTTP headers — then tell you if it's self-referencing, points elsewhere, is cross-domain, or missing. Catch duplicate-content and indexation issues before Google does. No sign-up.
Free, no sign-up. We read the page's rel=canonical from its HTML and HTTP headers, then tell you if it's self-referencing, cross-domain or missing.
What a canonical tag is & why it matters
A canonical tag (rel="canonical") is a single line in a page's HTML head that names the master version of that content. When the same page is reachable from several URLs — with tracking parameters, trailing slashes, uppercase variants, or print and AMP versions — the canonical tells Google which URL to index and rank, and consolidates link signals onto it instead of splitting them.
Get it wrong and you can quietly deindex pages, waste crawl budget on duplicates, or dilute the authority of your most important URLs. That's why a quick canonical check belongs in every publishing and migration checklist. For a deeper walkthrough, read our guide to canonical tags.
How to read your result
Self-referencing
The page points to its own URL. This is the correct, recommended setup for any standalone, indexable page — it removes ambiguity and is exactly what you want to see.
Points elsewhere / cross-domain
The canonical points to a different URL — another page on your site, or a different domain. Right for duplicates and syndicated content, but a red flag if this page should rank on its own.
Missing
No canonical found in the HTML or headers. Google will choose one for you. Add a self-referencing canonical to take back control, especially on parameterized or duplicate pages.
Common canonical mistakes — and how to fix them
Canonical to a redirected or 404 URL: the canonical points at a URL that redirects or no longer exists, so the signal is wasted.
Fix: always canonicalize to a live, 200-status final URL.
Multiple canonical tags: two or more rel=canonical tags on one page conflict, and Google may ignore all of them.
Fix: keep exactly one canonical tag per page.
Accidental cross-domain canonical: a template or migration leaves the canonical pointing at a staging or old domain.
Fix: point the canonical to the correct production URL on this domain.
Canonical fights other signals: the canonical says "index this" while a noindex tag, robots block or redirect says otherwise.
Fix: align canonical, robots, sitemap and internal links on one URL.
Find canonical issues across your whole site
A one-off check is great for a single page. SEOcrawl surfaces canonical and indexation issues straight from Google Search Console at scale — like "Alternate page with proper canonical tag" — so you can tag them via rules, manually or over MCP, and tie every issue to your rankings and traffic. See it all in one place instead of page by page.
FAQs
What is a canonical tag?
A canonical tag (rel="canonical") is a line in a page's HTML head that tells search engines which URL is the master version of that content. When the same or very similar content is reachable from several URLs, the canonical tells Google which one to index and rank, consolidating signals onto a single address.
How do I check a page's canonical?
Paste the page URL into the tool above and hit "Check canonical". We fetch the page, read the rel=canonical from its HTML head and its HTTP Link header, and tell you whether it's self-referencing, points to another page, is cross-domain, or is missing — with a pass/warn verdict. You can also view the source and search for "canonical" manually, but the tool also catches duplicate and conflicting tags.
What is a self-referencing canonical?
A self-referencing canonical is when a page's canonical tag points to its own URL. This is the recommended default for any standalone page: it removes ambiguity from tracking parameters, trailing slashes and uppercase/lowercase variants, and makes it explicit to Google that this URL is the one to index.
Does a missing canonical hurt SEO?
Not always, but it's a risk. Without a canonical, Google chooses one for you — usually the URL itself, but with duplicate or parameterized pages it may pick the wrong one or split ranking signals across versions. Adding a self-referencing canonical to every indexable page is a cheap, safe way to keep control.
