Many websites show the same content at several addresses without realising it. The same product appears with a colour parameter, with a Facebook tracking tag and at its clean address. The http and https versions both work. The www and non-www versions both load. To Google these are different URLs with identical content. The canonical tag tells Google which one is the real version.
What is a canonical tag
A canonical tag is a line in the head of a page: link rel canonical with the preferred URL. It tells search engines which version of a page to index and where to combine ranking signals. Most pages should have a self referencing canonical, meaning the tag points to the page's own clean URL.
What our checker shows
The Canonical URL Checker opens your page and reports:
- The canonical tag found on the page
- Whether there are multiple canonical tags, which confuses search engines
- Whether it is self referencing or points to a different URL
- Whether the canonical uses HTTPS
- Whether the canonical URL works with status 200 and no redirects
- Any canonical sent in the HTTP Link header
How to use it
- Open the Canonical URL Checker.
- Enter the page URL.
- Click Check Canonical.
- Fix any red or yellow checks.
Common canonical mistakes
- Missing canonical: add a self referencing canonical to important pages.
- Pointing every page to the homepage: a common theme bug that tells Google to ignore all your other pages.
- Canonical to a redirected or broken URL: always point to the final working URL.
- Canonical to http when the site uses https.
- Two canonical tags added by a theme and an SEO plugin at the same time.
When to point to a different URL
Use a canonical to another page when content is genuinely duplicated, for example:
- Product variants that share one main product page
- Printer friendly versions of articles
- Articles republished on a partner site, pointing back to your original
- URLs with tracking parameters, which should point to the clean URL. Clean them with the URL Parameter Remover.
Canonical is a hint, not a command
Google may ignore a canonical if other signals disagree, for example if internal links all point to a different version. Keep your internal links, sitemap and canonical tags consistent so they all point to the same preferred URL.
A real example
An online bookstore had every book page canonical pointing to the homepage because of a theme setting. Google indexed the homepage and ignored almost every book. The checker showed the problem on the first test. After changing the setting so each page used its own URL as the canonical, book pages started appearing in search within a few weeks. One wrong setting had been hiding thousands of pages.
Canonicals on paginated pages
Blog archives and category pages often have page two, page three and so on. Each paginated page should usually have a self referencing canonical, not one pointing back to page one. Pointing every page to the first page can stop Google from discovering the products or posts listed deeper in the series. Check a few paginated pages to confirm your theme handles this correctly.
Frequently asked questions
Does every page need a canonical tag
It is recommended for most indexable pages, especially on sites with parameters or duplicates.
Can a canonical point to another domain
Yes, for syndicated content, but use it carefully.
What is the difference between canonical and redirect
A redirect sends visitors to another URL. A canonical keeps the page visible but asks search engines to credit another URL.
Check your pages now with the free Canonical URL Checker.