What is a canonical tag?

A link element that tells search engines which URL is the authoritative version when the same content is reachable at several addresses, so ranking signals consolidate rather than splitting.

Can a canonical tag point to a redirect?

It can technically, but it should not. A canonical must resolve to a URL returning 200. Pointing at a redirect gives search engines contradictory signals and they may disregard the canonical entirely.

Should every page have a self-referencing canonical?

Generally yes. A self-referencing canonical is the safest default and prevents parameter and protocol variants from being treated as separate pages.

Canonical Tag Checker — Free Tool

Fetches the page and its canonical target. Some sites block automated requests — if that happens you'll see an error rather than a result.

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What a canonical tag is for

The same content is often reachable at several addresses — with and without www, with and without a trailing slash, with tracking parameters attached. A canonical tag tells search engines which version is the real one, so ranking signals consolidate instead of splitting.

Why "pointing at a redirect" breaks it

A canonical must resolve to a page that returns 200 OK. If it points at a URL that redirects, you've given search engines a contradictory instruction: this is the authoritative version, followed immediately by actually, go somewhere else. Google treats canonicals as a hint rather than a directive, and conflicting signals are exactly when it decides to ignore yours.

This happens more often than you'd expect, usually after a platform migration. It happened on this site: moving to a host that strips .html from URLs meant every canonical suddenly pointed at a 308 redirect. A crawl flagged 29 affected pages. The full write-up is in technical SEO examples — this tool exists because of that mistake.

What the checker looks at

Whether the URL itself redirects, and how many hops
Whether a canonical tag is present at all
Whether it's absolute or relative
Whether it's self-referencing
Whether the canonical target returns 200 or redirects
Whether a noindex directive makes the whole thing moot

Primary source: Google's documentation on consolidating duplicate URLs explains canonicalisation and the common mistakes, including canonicals that point at redirected or noindexed pages.

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