Canonical Tag
An HTML link element that tells search engines which version of a duplicate or similar page should be treated as the primary URL.
A canonical tag is an HTML <link rel="canonical"> element that tells search engines which URL is the preferred version of a page. It is used when the same or very similar content is available at multiple URLs, such as tracking-parameter URLs, filtered category pages, HTTP/HTTPS variants, or duplicate blog paths.
Canonical tags help consolidate ranking signals. If several URLs show the same content, Google may split signals across them unless a canonical URL clearly indicates which page should be indexed and ranked.
Best practices: use absolute URLs, make the canonical self-referential on the preferred page, point duplicate pages to the clean canonical URL, avoid canonical chains, and keep canonical tags consistent with redirects, internal links, and XML sitemaps. A canonical tag is a hint rather than an absolute directive, but conflicting signals can cause Google to ignore it.