A canonical tag is a <link rel="canonical" href="..."> element placed in the <head> of a page that names the preferred URL when the same or near-duplicate content is reachable from multiple addresses. It consolidates ranking signals and helps search engines pick a single version of the page to index and rank.
Why it matters
Without a canonical, tracking parameters, sort orders, session IDs, and protocol or trailing-slash variants can create many duplicate pages from one piece of content. Search engines may split link equity across these copies, index the wrong one, or skip them entirely as duplicates. A correct canonical funnels backlinks and crawl budget into one URL, which directly affects rankings, snippet selection, and how the page appears in results.
How to check
- View page source and confirm one
<link rel="canonical">in the<head>. - Make sure the canonical URL is absolute, uses
https, returns200, and is not noindex or blocked by robots.txt. - Confirm the canonical target appears in your sitemap.xml and is not stuck behind a redirect chain.
- For paginated or parameterised pages, decide whether each variant should self-canonicalise or point to a master URL — do not mix both.
- Check there is exactly one canonical per page; multiple tags are ignored.