JSON Schema Validator
Validate JSON data against JSON Schema specifications with Ajv. Instant client-side validation.
What is JSON Schema Validation?
A JSON Schema validator checks whether JSON data conforms to a defined contract — required fields, types, ranges, enums, and formats — not just that it parses. This tool is powered by Ajv (Another JSON Schema Validator), the standard fast validator used across the Node.js ecosystem, and runs it directly in your browser. Paste a schema on the left, your data on the right, and get precise, path-level error messages — with your documents never leaving your device.
Why use a schema validator?
Catch contract violations before they reach production: every failure reports the exact JSON path and what was expected (for example /user/age: must be integer). It's ideal for validating API request/response fixtures, CI configuration payloads, and forms data against their schemas. Running client-side means proprietary or pre-release schemas stay private, and validation speed is local — no network round-trip per check.
- Types — require string, number, boolean, object, array, or null
- Required fields — enforce mandatory properties
- Constraints — numeric ranges, string lengths, patterns, and enums
How to validate data against a schema.
- Paste your JSON Schema in the left editor (draft-07, 2019-09, or 2020-12 — detected from
$schema) - Paste your JSON data in the right editor
- Click "Validate Schema" to run Ajv locally
- Read the results — pass/fail with error paths and expected constraints
Use the "Valid Sample" / "Invalid Sample" buttons to see it in action, then continue via "Open in".
Related JSON tools.
A schema check is the second step — the first is confirming the data is valid JSON at all:
FAQ.
What is JSON Schema validation?
It verifies JSON data against a formal schema that declares required properties, data types, constraints, and formats — validating meaning and structure, not just syntax.
Which JSON Schema drafts are supported?
Validation is powered by Ajv: draft-07 by default, with 2019-09 and 2020-12 schemas detected automatically from their $schema declaration. Types, required, enums, patterns, and numeric/string constraints are all enforced.
Where is my schema and data processed?
Both are compiled and validated locally in your browser by Ajv running as JavaScript. Nothing is uploaded — pre-release schemas and sensitive data stay private.
How is this different from the JSON Validator?
The JSON Validator checks syntax (is it valid JSON?). This tool checks semantics (does it match your rules?). Use both: syntax first, schema second.
What do the error messages mean?
Each error names the JSON path that failed and the constraint it violated — for example /items/2/price: must be a number — so you can fix the data or relax the schema precisely.
Looking for a different transformation? Explore thefull JSON toolkit— 11 free, private, in-browser tools that never upload your data.