Handytool
DeveloperFreeRuns locally

JSON Schema validator

Validate JSON data against a JSON Schema — see every error with its path — privately in your browser.

.json
JSON Schema
0 lines0 bytes
Data to validate
0 lines0 bytes
Result
Click Validate to check the data against the schema.

About the JSON Schema validator

Handytool's JSON Schema validator runs Ajv, the most widely used JavaScript validator, locally in your browser. Paste a schema and a data document, click Validate, and you get either a green confirmation or a list of every failure with its instance path and message. Useful for testing API request bodies, OpenAPI examples, or configuration files before you ship them.

JSON Schema validator features

  • 01

    Powered by Ajv

    Ajv is the de-facto JavaScript JSON Schema validator. What passes here will pass in Node.js, Fastify, AJV-based linters, and most other JS toolchains.

  • 02

    All errors at once

    Configured with allErrors: true, so the result lists every failure rather than stopping at the first one — handy when fixing a malformed API payload.

  • 03

    Path-aware messages

    Each error includes the JSON pointer to the failing value, so you can jump straight to the offending field in a large document.

JSON Schema validator FAQ

Which JSON Schema drafts are supported?
Ajv supports drafts 6, 7, 2019-09 and 2020-12 out of the box. The default mode is non-strict, so most everyday schemas with type, properties, required, items, etc. work without extra setup.
Why does my $ref schema not load?
External $refs (URLs to other schemas) are not fetched in this browser-only tool. Inline all $defs and use local pointers like #/$defs/Address.
Is the schema or data uploaded anywhere?
No. Ajv runs entirely in your browser — both schema and data stay on your device.
Can I validate an OpenAPI spec with this?
Indirectly. OpenAPI's request/response bodies are JSON Schema fragments — paste a single body schema and the matching example data here. Validating the whole OpenAPI document requires a dedicated OpenAPI validator.

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