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Glossary › Canonical URL

What Is a Canonical URL?

A canonical URL tells search engines which version of a page is the “official” one when the same content exists at multiple web addresses. It is declared in a page's HTML using a rel="canonical" tag, preventing duplicate content from splitting ranking signals across multiple URLs.

Plain-English Definition

The same page can often be reached at multiple URLs. For example, a product page might be accessible at both example.com/shoes and example.com/shoes?color=blue. To a search engine, these look like two different pages with the same content — which dilutes the ranking signals both pages could earn.

The canonical tag solves this by pointing to the preferred URL. Google then consolidates all signals (links, crawl history) to that one URL and ranks it, rather than splitting authority between duplicates.

Why It Matters

Without canonical tags, a site can unknowingly compete against itself. E-commerce sites are especially vulnerable because sorting and filtering parameters create dozens of URL variants of the same page. Blogs can face the same issue if content is syndicated or if both HTTP and HTTPS versions of a URL are accessible.

Setting canonical URLs is a standard part of technical SEO. It ensures Google's crawl budget is spent on unique pages and that ranking signals flow to the right URL.

Example

A service business runs a blog and syndicates articles to a partner site. Without a canonical tag on the original article pointing back to their domain, Google might rank the partner's copy instead. Adding <link rel="canonical" href="https://example.com/blog/article" /> to both copies tells Google which one should get the credit.

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