Canonical URL
A canonical URL is an HTML element that tells search engines which version of a page is the original or preferred one when multiple URLs contain identical or very similar content.
Duplicate content is one of the most common SEO issues on the web. The same page can often be accessed through multiple URLs, with or without www, with different query parameters, through HTTP and HTTPS, or via URL variations created by tracking parameters, session IDs, or print-friendly versions.
Canonical tags are implemented as a <link> element in the <head> section of a page. Self-referencing canonicals (where a page points to itself) are considered a best practice because they proactively prevent duplication issues. Cross-domain canonicals can also be used when content is syndicated across multiple websites.
In practice
- An online store had 5 URL variations for each product (with tracking parameters, color selectors, etc.), adding canonical tags consolidated ranking power and improved positions by an average of 8 spots
- A blog syndicated content to Medium and other platforms, using cross-domain canonicals to ensure the original articles retained their search rankings
- A news site fixed their pagination canonicals so that page 2, 3, etc. of article listings didn't compete with page 1 in search results
- A travel website's filter system generated 10,000+ duplicate URLs, canonical tags reduced indexed pages by 80% and improved rankings for the remaining 2,000 important pages
Not sure how this applies to you?
A senior engineer walks your site, your search presence and the way enquiries reach you, then writes down the three things worth fixing first. You keep the document either way.