JSON Formatter & Validator
Developer Local only
JSON Schema Validator & Mock Data Generator
Local onlyValidate, infer, build, compare, mock, and convert JSON Schema and OpenAPI models.
Schema or OpenAPI document
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"title": "Product",
"type": "object",
"additionalProperties": false,
"properties": {
"id": {
"type": "integer",
"minimum": 1
},
"name": {
"type": "string",
"minLength": 2
},
"email": {
"type": "string",
"format": "email"
},
"tags": {
"type": "array",
"items": {
"type": "string"
},
"uniqueItems": true
},
"status": {
"enum": [
"draft",
"active",
"archived"
]
}
},
"required": [
"id",
"name",
"status"
]
}JSON instance
{
"id": 42,
"name": "Nobuf Toolkit",
"email": "hello@nobuf.com",
"tags": [
"browser",
"private"
],
"status": "active"
}Instance is valid
No validation errors were returned by the 2020-12 engine.
How to use it
- 01
Choose a dialect
Paste JSON Schema or an OpenAPI document, select a component model, and validate JSON with the matching Draft 7, 2019-09, or 2020-12 engine.
- 02
Build and test
Infer a schema from a sample, edit common fields visually, inspect JSON Pointer errors, and generate valid plus boundary test cases.
- 03
Convert and compare
Copy TypeScript or Zod output and review a conservative compatibility diff before evolving a schema.
Frequently asked questions
Which JSON Schema drafts are supported?
Validation uses separate Ajv instances for Draft 7, Draft 2019-09, and Draft 2020-12 so dialect vocabularies are not mixed.
Does it support OpenAPI?
It can detect an OpenAPI document and work with schemas under components.schemas. It does not claim to validate every path, operation, security scheme, or vendor extension in the full API document.
Is generated mock data random?
No. The built-in generator is intentionally deterministic, using const, enum, examples, defaults, constraints, and safe format examples where possible.
Is the compatibility report complete?
No. It flags common property, required-field, and type changes conservatively. Conditional schemas, references, custom vocabularies, and consumer behavior still need review.
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