Canonical Tag Checker

A canonical tag is a line in a page's <head>, <link rel="canonical" href="https://example.com/page/">, that tells search engines which URL is the preferred version of the page. The same content is often reachable at several addresses, through tracking parameters, filters, a trailing slash or www and non-www. The canonical says which one should be indexed and collect the ranking signals.

Google recommends a canonical on every page you want indexed. Without one, search engines pick the preferred URL themselves, which is usually fine but not always the version you would choose. The usual setup is a self-referencing canonical: the page points at its own clean URL.

It loads the page and reads every canonical signal: canonical tags in the HTML, a canonical in the HTTP Link header, and any noindex directive. It then checks how many tags there are, whether they sit inside the head, whether the URL is absolute, whether the tags and header agree, where the canonical points, and, when it points to another URL, whether that URL loads, redirects or returns an error.

It is a canonical that points at the page it is on. It is the normal, expected setup for the preferred version of a page, and it also protects the page if someone links to it with extra parameters, because the parameter version then points back to the clean URL.

A relative canonical such as href="/page/" works in Google, but it depends on the address the page was loaded from. An absolute URL with https and the domain removes any doubt, so we recommend it.

Usually not. If page 2 points its canonical at page 1, the products or posts that only appear on page 2 can be dropped from the index. Each page in a series normally has a canonical to itself.

Not necessarily. It is correct for duplicate versions of a page, such as parameter, filter or print versions, and for syndicated content you want credited to the original. It is a mistake if the page is meant to rank on its own, because you are telling search engines to prefer another URL.

No. A canonical is a strong hint, not a command. Google can choose a different URL if other signals, such as redirects, internal links, the sitemap or the content itself, disagree with it. To see which URL Google actually chose, open the URL Inspection tool in Google Search Console and look at "Google-selected canonical".

No. The tool reads the HTML the server sends, like a basic crawler. A canonical added later by JavaScript is not seen here, and Google advises putting the canonical in the HTML the server sends rather than relying on JavaScript.