What it looks like
A canonical tag is a link element in the head of a page.
<link rel="canonical" href="https://www.example.com/blue-widgets/">
The href holds the address you want search engines to treat as the main one. Use the full absolute URL, including https:// and the domain name.
The same page can often be reached at more than one address, for example with and without a tracking parameter.
https://www.example.com/blue-widgets/
https://www.example.com/blue-widgets/?utm_source=newsletter
Both addresses show the same content. The canonical tag on both should name the first one.
Why it matters
- It reduces duplicates. When several addresses show the same content, search engines keep one for indexing. The canonical tag lets you state which one you prefer.
- It gathers signals in one place. Links to the different versions are counted toward the main address.
- It is a hint, not a command. Google usually follows it, but it may choose another address if other signals disagree, for example when your XML sitemap lists a different version.
A canonical tag is not a redirect. Visitors stay on the address they opened. Only search engines act on it.
COMMON MISTAKEA canonical that points to the homepage from every page. Each page should normally point to itself.
How to check yours
- Open the page in your browser, right-click and choose View page source.
- Search the source for
rel="canonical". - Check that the address is absolute and that it is the page's own preferred address, unless the page really is a copy of another one.
- Run the free audit. It warns about a canonical that is missing, relative or pointing to another domain.
A canonical that names the wrong page is one of the usual reasons a page is missing from Google. The lesson crawling and indexing, explained simply lists the others.