Canonical URL
An HTML tag that tells Google which URL is the preferred version of a page.
A canonical URL is the address you have declared as the definitive version of a page, using a link rel="canonical" tag. It matters whenever the same content answers to more than one URL: without it, search engines pick a version themselves, and ranking signals split across the duplicates instead of accumulating on one.
Definition
A canonical URL tells search engines which version of a page is the "master" copy when multiple URLs serve similar or identical content. It's specified using the rel="canonical" link element in the HTML head.
Common scenarios: HTTP vs HTTPS, www vs non-www, URL parameters (filters, tracking), paginated content, and syndicated content. Without canonicals, Google may split ranking signals across duplicate URLs.
Across every site SlapMyWeb has audited, 60.2% declare a canonical URL — which leaves 39.8% with no canonical tag.
Measured from SlapMyWeb audits of live public URLs. The full aggregate is published as a CC-BY-4.0 dataset.
Why It Matters
Duplicate content dilutes ranking signals. If Google finds your page at 5 different URLs (with/without www, trailing slash, parameters), your backlink authority gets split 5 ways. Canonicals consolidate that into one URL.
Example
<link rel="canonical" href="https://slapmyweb.com/tools/word-counter" />This ensures all variations (HTTP, with parameters, etc.) point ranking signals to this one URL.
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