Canonical URL checker

What canonical tags actually do

A canonical tag is one line of HTML — <link rel="canonical" href="…"> — that tells Google which URL it should treat as the primary version when several URLs serve the same content. It's the single most powerful signal you have for consolidating duplicate-URL situations: query strings, trailing-slash variants, http/https mixes, paginated archives, and printable variants.

Without canonicals, Google has to pick one URL itself, and its choice may not be the version you want indexed. Worse, link equity gets split across the variants. A correct canonical keeps the equity consolidated on one URL and the others quietly drop out of the index.

How to build a clean canonical

A good canonical follows a small set of rules. The checker enforces them automatically so you don't have to remember.

• Use https://, not http://. Mixed-protocol canonicals fragment indexing.
• Strip query strings unless they produce genuinely different content (a search results page might keep them; a UTM-tagged blog post should not).
• Strip #fragments — Google ignores them for indexing anyway.
• Pick one trailing-slash convention site-wide and apply it consistently.
• Match the canonical URL in the tag exactly to the URL that returns 200 (no redirect chain).
• Use absolute URLs, not relative paths — the spec allows relative but absolute is safer.

Common canonical mistakes

The most expensive bug is pointing every page on the site to the homepage as canonical — usually a template error. Google then deindexes everything except the homepage. Always confirm self-canonicals on a fresh page.

Other frequent issues: canonicals pointing to a URL that 301-redirects somewhere else (defeats the purpose); canonicals with trailing-slash mismatches against the page's actual URL; and multiple canonical tags on the same page (Google picks one and warns in Search Console). When in doubt, render the canonical tag dynamically from the same URL builder you use for navigation.