Canonical Tag Checker
Verify the canonical URL of any page in real time. Detects missing tags, self-referencing errors, mismatched http/https or www variations, and cross-domain canonicals.
See exactly which canonical Google sees, not what you think you set
Canonical tags fail in surprisingly silent ways. The HTML source might say one thing, but the rendered DOM (after JavaScript executes) says another. Or your CMS injected a self-referencing canonical that contradicts the one you wrote. Or you have a canonical pointing to a redirect, which Google ignores.
This tool fetches any URL, executes JavaScript, and reports the EXACT canonical Google sees in the rendered DOM. It also flags the seven most common canonical mistakes, including the silent-but-fatal ones that most checkers miss.
Seven canonical errors that quietly destroy SEO
No canonical tag at all (Google has to guess, it usually guesses wrong on faceted/parameter URLs).
Multiple canonical tags on the same page (Google ignores all of them).
Canonical pointing to a 301 or 302 redirect (Google treats this as a soft signal at best, ignores at worst).
Canonical pointing to a 404 (the page is essentially uncanonicalised, duplicate content risk).
http canonical on an https page or vice versa (Google sees them as different URLs).
www vs non-www mismatch between canonical and rendered URL.
Canonical pointing to a different domain when you didn't intend syndication.
When to actually worry about canonical tags
You have parameter URLs (filters, sort orders, tracking)
E-commerce, real estate, job boards, anywhere with /products?color=red type URLs. Each parameter combination creates a near-duplicate URL. Without canonicals, Google wastes crawl budget and dilutes ranking signals across all variants.
You ran a domain migration (http→https or www→non-www)
Migrations frequently leave canonicals pointing to the old URL pattern. The 301 redirects work, but the canonical signal is wrong, and consolidation slows down.
You syndicate content (guest posts, partnerships)
When another site republishes your content, the cross-domain canonical from their copy back to yours is what tells Google your page is the original. Without it, the syndicating site can outrank you for your own content.
You have a JavaScript-rendered site
If your canonical is set client-side via JavaScript, it might not be in the initial HTML response that Google's crawler sees first. Always set canonicals server-side.