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JSON Schema Validator

Ajv-powered · drafts 04 / 06 / 07 / 2019-09 / 2020-12

Validate a JSON document against a JSON Schema. Draft auto-detected from the schema's $schema key — override if absent. Every error includes its data path, the failing keyword, expected vs actual, and a one-sentence explanation.

Paste schema and data.

How to validate

  1. Paste Schema in the top panel and Data in the bottom panel (or vice versa — use Swap).
  2. The draft is auto-detected from the schema's $schema key; override under Draft if missing.
  3. The verdict appears as a coloured banner. For invalid input, every error is listed with: path in the data, keyword that failed (type, required, pattern, …), expected, actual, and a one-sentence English explanation.
  4. All errors vs First error toggle controls verbosity.
  5. Copy errors as Markdown for ticket-friendly reports.

FAQ

Why does Ajv reject my schema?

The most common cause is a draft mismatch. If you wrote a 2019-09 schema and have draft-07 keywords (oneOf with sibling fields, etc.), it fails. Set the draft explicitly.

What about external $ref?

The validator doesn't fetch external $ref URLs (browser CORS would block them anyway). Inline the referenced schema, or use $defs.

Will it work offline?

Yes — Ajv is cached after first load.