Canonical Tag Checker

Page URL (optional)

Used to compare with canonical URL for self‑referencing.

Or paste HTML source

Canonical Check Result

Enter a URL or paste HTML, then click "Check".

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What is a Canonical Tag Checker?

A canonical tag checker scans a webpage's HTML for the <link rel="canonical"> element and helps you verify whether it is correctly implemented. The canonical tag tells search engines which version of a page is the master copy, preventing duplicate content issues. This tool extracts the canonical URL from any page—either by fetching the live URL (if CORS allows) or by pasting its source—and flags common problems like missing tags, multiple canonical declarations, or self‑referencing inconsistencies.

How to Use

Enter the page URL (optional) and click "Fetch URL" to automatically download the HTML. If the fetch fails due to CORS, manually paste the page's HTML source into the textarea.
Click "Check Canonical" to parse the HTML and extract all canonical link elements. The tool will show the canonical URL(s) found and compare them to the page URL if provided.
Review the status — a green message indicates one valid canonical tag, while warnings appear if the tag is missing, duplicated, or points to a different domain.

Frequently Asked Questions

Why does fetching the URL sometimes fail?

Many websites block cross‑origin requests for security reasons, so the browser cannot fetch the page content. The tool provides a fallback: you can paste the page's HTML source directly and check the canonical tags manually. This always works and keeps your data local.

Is my data safe? Does anything get uploaded?

Absolutely. All processing happens inside your browser. No URLs, HTML, or extracted canonical information is ever sent to a server, stored, or logged. You can check internal or staging pages without any risk.

What counts as a valid canonical tag?

The tool looks for standard <link rel="canonical" href="..."> elements in the <head>. It accepts both absolute and relative URLs (relative URLs are resolved against the page URL). It also detects the rarely used HTTP header form by checking for a meta tag equivalent (though header detection isn't possible client‑side).

Disclaimer: This tool performs all operations locally in your browser. No data is stored, transmitted, or logged.