Canonical tag
A canonical tag tells search engines which URL is the preferred version of a page when the same or very similar content is available at several addresses.
What is a canonical tag?
A canonical tag (rel="canonical") is an HTML element in the <head> of a page that tells search engines which URL is the preferred, “canonical” version of that content. It is used when the same or very similar content can be reached at several addresses – for example through URL parameters, tracking codes, print versions or product variants.
Without a canonical tag, search engines have to decide on their own which version to index. This can split ranking signals across duplicates, waste crawl budget and lead to the wrong URL appearing in search results. A canonical tag is a strong hint rather than a directive, so Google may still choose a different URL if other signals contradict it.
In international SEO, canonical tags and hreflang tags must work together. A common mistake is pointing the canonical tag of every language version to the main (often English) page. This tells search engines the translations are duplicates and can remove them from the index. Instead, each language or country version should reference itself as canonical and use hreflang to link to its alternates.