JSON Schema Validator (Draft 2020-12, Online)
Validate a JSON payload against a JSON Schema online. Supports Draft 2020-12, format validation (date-time, uuid, email, uri), and shows errors by JSON pointer path. 100% local — nothing is uploaded.
Last updated:
Payload matches the schema
All required fields present · all types and formats satisfied.
Validate a JSON payload against a JSON Schema (Draft 2020-12) online. Errors are reported by JSON Pointer path with clear messages. Supports format validation (date-time, uuid, email, uri) via ajv-formats. 100% local.
Tips & Best Practices
- ▸JSON Schema Draft 2020-12 is the latest — most modern tools (OpenAI structured output, Anthropic tool_use) use this or a subset.
- ▸For strict validation, use additionalProperties: false — otherwise unexpected fields silently pass.
- ▸The $schema keyword is optional but recommended; it lets other tools know which draft you're targeting.
Frequently Asked Questions
Which JSON Schema drafts are supported?
Draft 07, Draft 2019-09, and Draft 2020-12. The validator uses Ajv 2020 which is a strict superset — schemas without an explicit $schema keyword are treated as Draft 2020-12 by default.
Which format keywords are checked?
All formats from ajv-formats: date, date-time, time, duration, uri, uri-reference, email, ipv4, ipv6, uuid, regex, hostname, JSON pointer, and more. Unknown formats are ignored so schemas from other tools still parse.
Why does my payload fail with an OpenAI schema?
OpenAI strict schemas set additionalProperties: false and require every field. If your payload has extra keys or omits any listed in required it will fail. Use our JSON Schema Generator with 'Strict mode off' to produce a permissive variant instead.
Is my data uploaded anywhere?
No. Compilation and validation run entirely in your browser via Ajv. Both the schema and payload stay on your device.
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