Canonical Tag Checker
Inspect pasted page markup for canonical URL issues. Your work stays on this device whenever possible.
How to use Canonical Tag Checker
- Paste the page head, or the whole document, into "Page HTML or <head> Markup".
- Optionally add the address the page is served from in "Current Page URL (Optional)"; it enables relative-URL resolution and the self-referencing comparison.
- Press "Check Canonical" and read the Status line, which ends in VALID & OPTIMAL, WARNINGS DETECTED, CRITICAL ERROR or MISSING CANONICAL TAG.
- Compare the Declared Canonical with the Absolute Canonical, then read the Canonical Type line and the numbered checklist.
- Copy the corrected Ready Tag from the bottom of the result into your template.
Worked example
Paste a head containing <link rel="canonical" href="https://example.com/shoes"> and set the current page URL to https://example.com/shoes?color=blue. The result shows Status VALID & OPTIMAL, both canonical lines equal to https://example.com/shoes, and Canonical Type Consolidating Parameters. The checklist confirms a single tag, an absolute HTTPS address and no conflicting tags.
When to use this tool
- Verifying that filtered product URLs point back to the clean category page.
- Catching a duplicate canonical injected by both a theme and an SEO plugin.
- Checking a relative canonical before a site moves to a new domain.
Important limitations
Checks HTML markup declarations. If canonical URLs are simultaneously declared via HTTP Link headers on the web server, both sources should be cross-referenced to prevent conflicting directives.
Frequently asked questions
What is flagged as a critical error?
Finding more than one canonical link element. Conflicting tags can lead search engines to ignore all of them, so the tool ranks it above the other findings.
Which other issues does it report?
A relative path in the href, an http:// target, and a fragment containing a hash sign. It also reports a missing tag and suggests a self-referencing one, using your current page URL if you supplied it.
What does Consolidating Parameters mean?
Your current page URL and the canonical share the same host and path but differ in the query string, as with tracking or filter parameters. The tag then points to the clean version, which is the usual intention.
Does it check the canonical target itself?
No requests are made. It does not test whether the target returns 200, is indexable, redirects, or points back to another canonical. Those checks need a crawl or a live header tool.
Does an HTTP header canonical count?
Only HTML markup is analysed, so a declaration sent in a Link response header is not seen. If your server uses headers, inspect them with the HTTP header checker.