Free tool
Free Canonical Tag Checker
Learn more: Duplicate Content and Canonical Tags Explained
Why canonical tags matter
When the same or near-identical content exists at more than one URL, search engines have to pick one version to index and rank. The canonical tag is how you tell them which one — leave it wrong or missing, and they'll guess, sometimes choosing a URL you didn't want indexed at all.
Common canonical tag problems
- Self-referencing canonical missing — every indexable page should canonicalize to itself by default; without it, engines fall back to their own signals.
- Canonical points to a URL that redirects or 404s — a broken chain wastes the canonical signal entirely.
- Canonical points to a different page's content — often a leftover from copying a template or a CMS misconfiguration.
- Parameters or tracking tags create unintended duplicates (like ?utm_source=) without a canonical tying them back to the clean URL.
- Pagination or filtered/sorted views all canonicalize to page 1 when they actually contain unique content — this can hide real pages from the index.
How to fix it
- Make sure every indexable page has a canonical tag, and that it points to itself unless there's a genuine duplicate elsewhere.
- For true duplicates (print versions, session-ID URLs, tracking parameters), canonicalize to the single clean version you want indexed.
- Never canonicalize a page to a URL that redirects, errors, or is itself noindexed — check the chain resolves to a live, indexable page.
- For a deeper look at when duplicate content is actually a problem and how canonical tags interact with it, see duplicate content and canonical tags.
Frequently asked questions
Does the canonical tag guarantee which URL gets indexed?
No — it's a strong signal, not a directive. Google can and sometimes does choose a different URL as canonical if other signals (internal links, redirects, sitemap) point elsewhere.
Should every page canonicalize to itself?
Yes, by default. A self-referencing canonical is the normal, expected state for any page you want indexed as-is — it isn't a sign of a problem.
Can a wrong canonical tag deindex a page?
Yes — if page A canonicalizes to page B, search engines may stop considering page A for indexing altogether and consolidate signals onto page B instead, even if that's not what you intended.
What's the difference between a canonical tag and a redirect?
A redirect sends visitors and crawlers to a different URL entirely — the original stops being reachable. A canonical tag keeps both URLs live and reachable, it just tells search engines which one to treat as authoritative for indexing and ranking.