Overview
This page is the atomic definition. The contextual deep-dive lives at technical.
Definition
A canonical URL is the single authoritative URL for a piece of content. When the same content is reachable at multiple URLs (with and without trailing slash, with tracking parameters, across protocols), the canonical URL is the one the site owner wants search engines to index and rank. The signal is declared with <link rel="canonical" href="https://example.com/page"> in the HTML head, an HTTP Link header, or a <loc> entry in the XML sitemap. Search engines treat the canonical as a strong hint, not a directive.
When it applies
Set a canonical URL on every indexable page. It matters most when faceted navigation, pagination, tracking parameters, or syndication produce multiple URLs for the same content.
Example
A product page is reachable at /products/widget, /products/widget?ref=email, and /products/widget?utm_source=ads. All three include <link rel="canonical" href="https://example.com/products/widget"> so Google consolidates ranking signals onto the clean URL.
Related concepts
- technical - the broader technical SEO checklist that includes canonicals.
- crawl-budget - canonicals protect crawl budget by deduplicating fetches.
- content - content-side rules that pair with canonical signals.
- internal-linking - link to the canonical URL, not parameterized variants.
- structured-data - schema markup that pairs with canonical declarations.
Citing this term
See Canonical URL (llmbestpractices.com/glossary/canonical-url).