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Canonical Checker Tool

Paste a page’s HTML source to extract and validate <link rel="canonical">. This runs fully offline (no fetching), flags duplicates and missing/invalid hrefs, resolves relative canonicals when you provide a page URL, and compares with og:url.

Category: SEO · URL: /tools/canonical-checker-tool.html
Used to resolve relative canonicals and compare canonical vs page URL.
No network calls. This tool reads your pasted HTML and highlights common canonical issues (missing/duplicate canonicals, invalid/relative hrefs, fragments, and og:url mismatches).
Output will appear here.
Related tools:
Robots Checker Google (Offline) Robots Checker Online (Offline) Free Sitemap Generator Tools Free Sitemap Generator Tool (XML) Schema Checker Google (Offline) Schema Checker Tool (JSON-LD) Schema Checker URL Builder Schema Checker
Privacy: runs locally in your browser. No uploads, no tracking scripts.

How to use

Tip: Use “View page source” and paste the raw HTML (not the rendered DOM) for the cleanest result.

  1. (Optional) Enter the page URL to resolve relative canonicals and compare against the page.
  2. Paste the HTML into the box.
  3. Click Check Canonical.
  4. Review the summary and flagged issues, then copy the report if needed.
Keywords this page targets (natural cluster): canonical checker tool, check canonical tag, rel canonical checker, canonical url checker, canonical tag validator, find canonical url in html, detect multiple canonical tags, canonical tag missing checker, relative canonical url resolver, canonical vs page url check, canonical vs og:url mismatch, canonical link element parser, canonical tag audit, validate canonical href, canonical tag troubleshooting, seo canonical checker offline, canonical url normalization check, canonical tag extractor, self-referencing canonical check, canonical tag best practice check
Secondary intents covered: Extract the canonical URL from pasted HTML source, Detect multiple or conflicting canonical tags, Validate canonical href presence and URL format (http/https), Resolve relative canonical URLs using a provided page URL or <base href>, Compare the canonical URL to the page URL to spot mismatches, Check whether og:url matches the canonical URL, Generate a quick report you can copy into an audit note, Spot common canonical issues like fragments (#) or non-HTTP schemes

FAQ

What does this canonical checker do?

It parses pasted HTML to find rel="canonical", shows the canonical URL(s), and flags common issues like duplicates, missing hrefs, or non-http(s) URLs.

Does this tool fetch a URL or crawl my site?

No. It runs offline and only analyzes what you paste, so it can’t verify server responses or whether the target URL exists.

Why should there usually be only one canonical tag?

Multiple canonicals can send conflicting signals; Google may ignore them or choose one unpredictably.

Are relative canonical URLs allowed?

They can work, but absolute canonicals are safer. This tool can resolve relative values if you provide a page URL (or the HTML has <base href>).

What if my canonical differs from the page URL?

That can be correct for duplicate/parameterized pages. The report marks it as info so you can confirm it’s intentional.

Why check og:url against the canonical?

If og:url and canonical disagree, social sharing and SEO signals can become inconsistent; aligning them is usually cleaner.

Does it detect canonicals in HTTP headers (Link: rel=canonical)?

No—only HTML. Header-based canonicals require a fetch, which this offline tool intentionally does not do.