What is a canonical URL?
Definition
A canonical URL is the one version of a page you want search engines to treat as the original, when the same content loads at several addresses.
The same page can often load at several URLs: with and without a trailing slash, with tracking parameters, over http and https, or through a script path like /index.php. To a search engine each is a separate address, and the signals a page earns can split between them.
A rel="canonical" link tells Google which version you prefer. Google calls it "a strong signal", not a command, and still chooses the canonical itself, weighing it alongside redirects, internal links, and sitemaps. The most reliable fix for a true duplicate is a permanent 301 redirect to the one clean URL, backed by a canonical tag and consistent internal links. This site redirects every duplicate form of its URLs to the clean version for exactly that reason.
Why does it matter to your business?
Duplicate URLs quietly split the credit a page earns. One address per page keeps every link and signal pointing at the version you want to rank.
Related terms
Sources, verified September 11, 2026
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