Canonical URL checker. The one truth.
Paste your page HTML. The tool extracts rel=canonical, checks for absolute URL form, HTTPS, and the duplicate-declaration trap that splits Google's signal across two URLs. Pure browser code — no fetch, no log.
Paste your page HTML in the textarea. The right panel extracts every <link rel="canonical"> tag, validates absolute / HTTPS / non-duplicate, and outputs the canonical URL plus pass/warn/fail line for each rule.
Tip: in Chrome DevTools → Elements panel → right-click <html> → Edit as HTML → copy the entire string.
Sources used by this checker
- Google canonicalization spec
- RFC 6596 — The Canonical Link Relation
- Self-referential canonical is the safest default per Google's recommendation.
Privacy: HTML parsed in-browser only.
Six questions users ask.
Why does my page need a canonical tag?
When the same content lives at multiple URLs, Google has to pick one as the indexed version. Without a canonical tag, Google guesses — and sometimes guesses wrong. The canonical tag tells Google which URL is the master version, consolidating link equity and ranking signals.
Should the canonical match the current URL?
Almost always, yes. Self-referential canonical tags are the safest pattern. The exception: pagination, faceted-navigation pages, and printable versions point their canonical to the parent.
Why is absolute URL required?
Relative canonicals technically work but break in edge cases — when the page renders on a different domain (staging, AMP cache, syndicated), the relative URL resolves wrong. Google's docs say always use absolute.
Can I have two canonical tags?
No. Multiple rel=canonical declarations on a single page is a known SEO bug — Google's parser handles it inconsistently. Pick one source of truth.
Should canonical use https://?
Yes. Even on a fully-HTTPS site, an http:// canonical splits indexing signal between the two protocols.
Does this tool log my HTML?
No. The form runs entirely in JavaScript on your device. Nothing is sent to Digital Heroes servers.
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