SEO tools
Canonical Checker
Fetch a URL and read back every signal that decides whether and how it gets indexed: the canonical tag, the robots meta, the X-Robots-Tag header and og:url — with the contradictions between them called out.
Where the signals live
Indexing is decided by four separate mechanisms in three different places. Checking only the page source catches two of them, which is why a page can look correct and still be missing from search.
| Signal | Where it lives | Strength |
|---|---|---|
| rel=canonical | HTML head, or Link header | Hint |
| robots meta | HTML head | Directive |
| X-Robots-Tag | HTTP response header | Directive |
| Sitemap inclusion | sitemap.xml | Weak hint |
The distinction in the last column is the practical one. A directive is obeyed; a hint is weighed against everything else Google knows. That is why a canonical can be overruled by strong internal linking to a different URL, while a noindex is simply respected.
Related tools
- Redirect Checker — a canonical to a redirecting URL wastes the signal entirely.
- Meta Tag Generator — generate a corrected head block once you have found the problem.
- Robots.txt Generator — the crawl-level counterpart to these page-level directives.
Frequently asked questions
What is a self-referencing canonical and do I need one?
It is a canonical tag that points at the page's own URL. You do not strictly need one — Google can work it out — but it is cheap insurance. It settles which version wins when the same page is reachable with tracking parameters, a trailing slash, or over both http and https.
Is the canonical tag a directive?
No, it is a hint. Google can and does ignore canonicals it disagrees with, particularly when the two pages are not genuinely duplicates or when internal links and sitemaps point the other way. If Google picked a different canonical, the URL Inspection tool in Search Console will tell you which one and why.
Why is combining noindex with a canonical a problem?
They give contradictory instructions. A canonical says 'consolidate this page's signals into that other URL'; noindex says 'do not index this at all'. Google has warned that it may end up applying the noindex to the canonical target as well, which can de-index the page you actually wanted to keep. Choose one.
Can a canonical point to another domain?
Yes, and it is legitimate for syndicated content — the syndicating site canonicalises to the original publisher. It is also a common symptom of a hacked site, so an unexpected cross-domain canonical is worth investigating rather than assuming it was intentional.
Does the X-Robots-Tag header override the meta tag?
They combine, and the most restrictive wins. A noindex in either place will keep the page out of the index. The header catches people out because it is invisible in the page source — this tool reports both, which is why a page that looks fine in view-source can still be marked noindex here.
Should og:url match the canonical?
Yes, in almost every case. They are answering the same question — what is the real address of this page — for two different audiences. When they disagree, shares and search results attribute the same content to two different URLs, which splits the signals you were trying to consolidate.