h2check

Validate JSON against a schema

Paste a JSON Schema and a document to see whether the document validates, and exactly which instance paths fail. Validation runs in your browser.

What it checks

  • Which draft the schema declares, or that it declares none.
  • Whether the document validates.
  • Every failing keyword with the instance path it failed at, not only the first one.
  • The parameters of each failure, such as the limit a number exceeded or the property that was not allowed.
  • Format keywords such as email, uri and date-time.

What is not stored

Nothing is stored and nothing is sent. This checker is JavaScript that runs inside your browser tab, so the value you paste never reaches h2check.org or any other server. Close the tab and it is gone.

Limits

  • External $ref targets are not fetched. Inline every referenced schema before validating.
  • A schema with no $schema keyword is validated as draft-07. A validator in your pipeline may assume a different draft and disagree.
  • Passing here means the document matches this schema. It does not mean your service accepts it.

Procedures that explain the result

Put it on your own page

Link to it with the value filled in, and the checker runs as soon as the page opens.

<a href="https://h2check.org/tools/json-schema/">Validate JSON against a schema</a>