Canonical URL: what it is and why it's needed

What is a canonical URL

A canonical URL (canonical link) is an HTML element <link rel="canonical" href="..."> that tells search engines which version of a page to treat as the primary one. This is critical when the same content is available at multiple URLs.

Why canonical is needed

Duplicate content is one of the most common SEO problems. It occurs when:

• A page is available with and without www
• URLs have sorting or filtering parameters (?sort=price&page=2)
• The site has HTTP and HTTPS versions
• There is a trailing slash (/page/ vs /page)

Without canonical, search engines may:

• Index the wrong version
• Split link equity among duplicates
• Lower rankings due to duplicate content

How to configure it correctly

Add this to the <head> of each page:

<link rel="canonical" href="https://example.com/page" />

Usage guidelines

1. Canonical should point to itself — even if there are no duplicates, using a canonical link to the current page is best practice
2. Use absolute URLs — https://example.com/page, not /page
3. Use one canonical per page — multiple tags will cause confusion
4. Canonical on paginated pages — each paginated page should point to itself, not to the first page

Check canonical with reChecker

Use the Canonical Checker to check canonical URLs on any site. The tool shows:

• Whether a canonical tag is present
• Whether the URL is valid (absolute and valid)
• Whether it matches the page's current URL
• Whether there are conflicts with the HTTP Link header

FAQ

What's the difference between canonical and noindex? Canonical directs indexing to another page, while noindex completely excludes a page from the index. Use canonical for duplicates and noindex for pages that should not appear in search results.

Does canonical affect crawling? No, canonical does not prevent crawling — it only indicates the preferred version for indexing. Use robots.txt to block crawling.