Canonical tag
Also known as: rel=canonical, canonical URL, canonical link element
A canonical tag is an HTML element — <link rel="canonical" href="..."> — that tells search engines which URL is the preferred version of a page when several URLs show the same or similar content. It consolidates ranking signals onto one URL and prevents duplicate-content dilution.
- Set with <link rel="canonical"> in the page head
- Consolidates duplicate URLs onto one preferred address
- A hint to search engines, not an absolute rule
What the canonical tag does
A canonical tag lives in the page <head> and points to the URL you want indexed. When the same content is reachable through multiple addresses — `http` and `https`, with and without a trailing slash, or with tracking parameters — the tag tells search engines to treat your chosen URL as the master and credit it with the ranking signals.
It is a strong hint, not a hard directive. Search engines usually honor it but can ignore a canonical that conflicts with other signals, such as internal links and sitemaps pointing elsewhere.
Common mistakes
A self-referencing canonical (a page pointing to itself) is normal and recommended. Problems arise when every page points to the homepage, when the canonical URL returns an error or redirect, or when it uses a relative path instead of an absolute one.
Keep canonicals consistent with your other signals: the canonical URL should be the same address you list in your sitemap and link to internally.