Canonical URLs Explained: How to Fix Duplicate Content
Understand canonical URLs, duplicate and near-duplicate pages, common canonical mistakes, and how to implement canonical tags correctly.
What Is a Canonical URL?
A canonical URL identifies the preferred version of a page when multiple URLs represent the same or very similar content. The canonical link element is commonly placed in the HTML head.
<link rel="canonical" href="https://example.com/example-page">Why Canonicalization Matters
Websites can create multiple URL versions through query parameters, filters, tracking parameters, trailing-slash conventions, HTTP/HTTPS differences, and other URL patterns.
Common Canonical Mistakes
Canonical Points to a Redirect
Whenever possible, make the canonical URL the final preferred URL rather than a URL that redirects elsewhere.
Canonical Points to the Wrong Page
Each canonical should represent the content of the current page. A site-wide canonical pointing to the homepage can cause important pages to be misunderstood.
Inconsistent URL Variants
Keep protocol, hostname, path, and trailing-slash conventions consistent.
Canonical vs Redirect
A redirect tells the browser and crawler to go to another URL. A canonical tag provides a preference while leaving the current URL accessible. They solve different situations.
For a complete technical review, see our technical SEO audit checklist.
Conclusion
Canonicalization is about consistency. Decide which URL version represents the page and use that preference consistently across internal links, sitemaps, and canonical tags.