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Canonical Tag Checker Guide

Understand canonical URLs and how to check them before publishing or refreshing SEO pages.

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SEO guide

What is a canonical tag checker?

A canonical tag checker helps you confirm that a page sends a clear indexing signal. It is useful before publishing new pages, migrating URLs, adding filters, or debugging duplicate-content warnings.

What is a canonical tag?

A canonical tag is an HTML link element that tells search engines which URL is the preferred version of a page. It is commonly used when similar or duplicate content can be reached from multiple URLs.

What does a canonical tag checker do?

A canonical tag checker inspects a page source for rel canonical links and reports whether the canonical URL is missing, duplicated, invalid, relative, or different from the expected URL.

How this tool works

The MTKits checker reads pasted HTML in your browser, extracts link tags, looks for rel values that include canonical, validates the href, resolves relative URLs against the page URL, and compares the result with the expected canonical URL.

Why it matters for SEO

Clean canonical tags help search engines consolidate duplicate page signals, choose the right URL for indexing, and avoid splitting ranking signals across tracking, filter, print, or alternate URL versions.

Issues the checker can catch

  • Missing canonical tag
  • More than one canonical tag
  • Canonical tag without an href value
  • Invalid canonical URL
  • Relative canonical URL that should be absolute
  • HTTP canonical URL on an HTTPS page
  • Canonical URL mismatch against the expected URL

Recommended canonical tag format

Place one canonical link in the page head. Use the final public URL you want search engines to treat as the preferred page.

<link rel="canonical" href="https://example.com/preferred-page" />