How do I check canonical tags online?

Enter a URL into the Canonical Tag Checker and review the HTML rel=canonical and any Link rel=canonical header. The tool flags missing, duplicate, and cross-domain issues and offers fixes.

What happens if canonical tags are wrong?

Incorrect or conflicting canonicals can dilute link equity, cause duplicate content, and confuse search engines about which URL should rank.

Is rel=canonical required on every page?

It’s not mandatory, but recommended for most indexable pages—especially when duplicates or URL variants might exist.

Should the header canonical match the HTML tag?

Yes. If you use both, the header Link rel=canonical should match the HTML canonical to avoid conflicting signals.

Canonical Tag Checker

Instantly validate your page’s <link rel="canonical">. Detect missing, duplicate, cross-domain, and header Link rel="canonical" issues — fast and free.

Also try our Meta Title & Description Checker for a quick snippet audit.

What Is a Canonical Tag Checker?

A Canonical Tag Checker is an SEO tool that scans your page’s HTML for the <link rel="canonical"> element and optional Link: <...>; rel="canonical" HTTP header. Canonical tags tell search engines which URL is the preferred version to index when duplicate or near-duplicate content exists.

Why Canonical Tags Matter for SEO

Prevent duplicate content and keyword cannibalization.
Preserve and consolidate link equity to the canonical URL.
Reduce wasted crawl budget on duplicate URLs (with parameters, casing, or trailing slashes).
Clarify signals across cross-domain or migrated content.

How to Use This Canonical Tag Checker

Enter the full page URL (e.g., https://example.com/page).
Open Advanced Options to follow redirects, check header canonicals, or show raw headers.
Click Check Canonical to view issues and recommendations.

Common Canonical Tag Issues & Fixes

Missing canonical: Add a single <link rel="canonical" href="..."/> in the <head>.
Multiple canonicals: Keep exactly one HTML canonical per page (plus optional matching header).
Relative canonical: Use absolute URLs (with scheme + host).
Cross-domain mismatch: Avoid pointing to a different host unless it’s intentional.
Noindex + canonical: Don’t combine; engines may ignore the canonical.
Non-200 target: Canonical target should resolve to 200 OK, not 3xx/4xx/5xx.

Pro tip: Standardize your final URL structure (protocol, host, trailing slash) and ensure your canonical matches the final resolved URL.