Find Missing or Multiple Canonical Links in Source

How to Use This Tool

Inspect canonical declarations without assuming the current browser URL. Check pasted HTML locally for a missing, single or multiple canonical link declaration and show the declared URL.

The failure HTML Canonical Check is designed to catch

A canonical is a hint in source, not proof that indexing systems selected it, but duplicates are an immediate implementation defect. The boundary is the job stated in Find Missing or Multiple Canonical Links in Source; HTML Canonical Check is not intended to score or transform a different workflow.

The HTML Canonical Check input contract

The fields used for this specific operation are Input text, Unused option. Keep the source values beside the HTML Canonical Check result, because replacing the original would remove the evidence needed to reproduce or reverse the operation.

• For HTML Canonical Check, Input text starts at <link rel="canonical" href="https://example.com/page"> in the worked case; replace that example with the matching source value.
• For HTML Canonical Check, Unused option starts at in the worked case; replace that example with the matching source value.

Worked result for HTML Canonical Check

The executable case called Default browser-only example expects out: Canonical: https://example.com/page. Verify that observation before entering real material, and then change one HTML Canonical Check field at a time so an unexpected direction or formatting change can be traced to a specific input.

Reading the HTML Canonical Check output

No. The transform runs in browser JavaScript and the page does not call a processing API. Network extensions or a compromised device remain outside this page's control. Apply that answer only when Input text, Unused option describe the same scope and format as the worked operation. If the source uses different units, quoting, nesting, timing or account rules, a plausible-looking HTML Canonical Check output is not sufficient validation.

Assumptions attached to HTML Canonical Check

• HTML Canonical Check assumes that the pasted input uses the syntax described by the selected standard or page guidance.
• HTML Canonical Check assumes that the operation is intentionally narrow and does not infer private downstream schema rules.

If one of these HTML Canonical Check assumptions is false, keep the result as a diagnostic rather than production or decision data, and choose an implementation that explicitly supports the missing rule.

Evidence maintained for HTML Canonical Check

The recorded reference is WHATWG HTML Living Standard. Reopen that source when the definition, format, fee or policy behind HTML Canonical Check changes; private configuration and downstream acceptance still have to be checked in the user's own system.

Where HTML Canonical Check runs

The named operation executes in browser JavaScript without an ecech calculation API. For HTML Canonical Check, local execution reduces transmission but does not control browser extensions, device security or the destination where the result is pasted, so sensitive inputs still require the user's normal handling rules.