What is a canonical tag?
SEO Definition and Examples
The canonical tag (rel="canonical") tells Google the main version of a page when similar or duplicate URLs exist, preventing duplicate-content penalties.
Full Definition: What is a canonical tag
The canonical tag is an HTML element (<link rel="canonical" href="URL"/>) placed in the page's <head> that signals to Google that this is the "preferred" or "canonical" version of the content. It is essential when the same content appears at different URLs (with and without www, with URL parameters, http vs https, with/without trailing slash). Every page should have a canonical pointing to itself (self-referencing canonical) or to the main version.
Why Does Canonical Tag Matter for SEO?
Without a canonical, Google can decide on its own which version of your page is the "original" — and may choose wrong. Unresolved duplicate content can dilute ranking authority across versions and lead to penalties. Google confirms that correct canonicalization is essential for efficient indexing.
Source: Google Search Central — CanonicalFrequently Asked Questions about Canonical Tag
Related Terms
Technical SEO
AdvancedTechnical SEO covers your site's infrastructure — crawlability, indexing, loading speed, HTTPS and data structure — that lets Google find and understand pages.
Robots.txt
IntermediateRobots.txt is a text file placed at the root of a site that tells crawlers (Google, Bing, GPTBot) which pages they may or may not access and index.
XML Sitemap
BeginnerAn XML sitemap is a file that lists all the important URLs of your site, helping Google discover and index them faster and more completely.
Crawlability
IntermediateCrawlability is the ability of Google's robots to access, navigate and read your site's pages — an essential prerequisite for indexing and ranking.
Put Canonical Tag into practice
Explore how to apply this concept to your industry and city.
