What is a canonical URL?
The same page can often be reached at several addresses: with and without www, with a trailing slash, with a tracking code on the end. To search engines these can look like duplicate pages competing with each other. A canonical tag names the one official address. It is a single line in the page head and most platforms add it automatically, but it is worth checking it points to the right version.
Why it matters
If Google finds your home page at four addresses, it may index all four and divide the links and ranking between them, or pick the one you would not have chosen. A canonical tag tells it to treat all the variants as one page at the address you name, and to credit that address with the links. It matters most for shops, where filtered and sorted versions of a category page can produce hundreds of near-duplicates.
Common mistakes
- A canonical pointing to the http version after the site moved to https.
- A canonical pointing to the old domain after a domain change.
- Every page's canonical pointing to the home page, which tells Google to ignore every other page.
- A canonical on the staging site copied to the live site.
How to check
Our check reads the canonical tag on your home page and reports whether it matches the address that loaded. View the page source and search for "canonical" to see it yourself.
How to fix it
On WordPress, both the core and SEO plugins add a canonical tag automatically, using the site address in Settings, General, so make sure that address is the https version you want. On other platforms it is usually automatic too. If the tag is missing or wrong, an SEO plugin lets you set it per page. The canonical should always be an absolute address, including https and the domain.
Not sure how your own site does on this? Run the free check: it takes about twenty seconds and reports on this and thirty other things.