JSON Schema validator — check data against a schema
Paste a JSON Schema and a JSON document and see whether the data is valid, with a clear per-path list of any problems. It validates entirely in your browser (0 uploads, works offline).
How to use it
- Paste your JSON Schema on the left and the JSON data on the right.
- The result appears live — either valid, or a list of the exact paths that fail and why.
- Copy or Download the validation report.
FAQ
How do I validate JSON against a schema for free?
Paste the schema and the data. This page checks types, required properties, enums, numeric ranges, string length, patterns and additional-property rules, then reports each failing path — for example age: must be ≤ 150. It runs on your device with no upload.
Which JSON Schema features are supported?
A practical subset of draft 2020-12: type, required, properties, items, enum, minimum, maximum, minLength, maxLength, pattern and additionalProperties. It covers the rules most everyday schemas use.
Is my data uploaded anywhere?
No. Both the schema and the data are validated entirely in your browser and nothing is transmitted or stored — you can verify that by turning off your Wi-Fi. Sensitive payloads stay on your device.
Why does it say a property is unexpected?
When the schema sets additionalProperties to false, any property not named in properties is reported as unexpected. Remove the property or add it to the schema.
Limits
Implements a common subset of JSON Schema; advanced keywords such as $ref, allOf, if/then and format assertions are not evaluated.
Related
The JSON formatter tidies a document; the JSON-to-TypeScript tool turns a sample into types.
Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.