Canonicalization
The process by which a search engine groups duplicate or near-duplicate URLs into a cluster and picks one representative URL to index and…
Crawling IndexingCanonical tagCanonical link element
rel="canonical"
A link annotation (in the head or an HTTP header) that tells search engines which URL you consider the preferred version of duplicate content.
In full
Specified in RFC 6596, rel=canonical can be delivered as `<link rel="canonical" href="...">` in the HTML head or as a `Link:` HTTP header for non-HTML files such as PDFs. It should be self-referential on canonical pages and absolute rather than relative. Conflicting signals — a canonical pointing at a noindexed page, a canonical chain, or canonicals contradicting sitemaps and internal links — cause search engines to ignore the hint.
Example
A printable version at `/article/print` carries `<link rel="canonical" href="https://example.com/article">` so only the main article is indexed.
Related terms
Duplicate content
Substantively identical or near-identical content available at more than one URL, within a site or across sites.
Pagination
Splitting a long list or article across sequential URLs; Google stopped using rel=next/prev for indexing in 2019 and treats each page…
noindex
A robots directive, delivered by meta tag or X-Robots-Tag header, that instructs search engines to drop a page from their index.
hreflang
An annotation declaring alternate language or regional versions of a page, so search engines serve the appropriate one to each user.