JSON Schema Generator
Automatically generate JSON Schema from your data
The JSON Schema Generator reads a sample JSON document and produces a valid Draft-07 schema describing its structure — types, nested objects, arrays, required fields, and enums. It is built for API developers who want request validation or contract tests without handwriting a schema, and for teams documenting their JSON payloads.
How to Use
- Paste your JSON: Drop a sample API response or config object into the input.
- Generate: The tool walks the structure and infers a schema for every node.
- Review the output: Check detected types, required fields, and enum candidates.
- Copy the schema: Use it with Ajv, Python’s jsonschema, or your docs pipeline.
Features
- Generates Draft-07 output with the $schema declaration
- Distinguishes integer from number, and detects null values
- Recurses through nested objects and arrays of any depth
- Marks fields required when they appear in every array element
- Suggests enums for fields with a small set of repeated values
What is JSON Schema?
JSON Schema is a vocabulary for describing what a JSON document may look like. A schema can declare that user.name must be a string, that user.age must be an integer, and that both are required. Validators such as Ajv (JavaScript) or jsonschema (Python) can then check incoming payloads against that contract and reject malformed data before it reaches your business logic.
A generated schema is a starting point, not the finished product. Inference can tell that a field held an integer in your sample, but it cannot know the value should be at least 0, or that a string must match an email format. Review the output and add constraints like minimum, maxLength, pattern, and format that reflect your real rules. And give the tool a rich sample: fields missing from your JSON cannot appear in the schema.
Use Cases
- API development: Bootstrap request/response validation from a real payload.
- Contract testing: Generate a baseline schema, then diff it as the API evolves.
- Documentation: Produce schemas for developer portals and OpenAPI specs.
- Data pipelines: Validate config files against an inferred structure.
Related Tools
Frequently Asked Questions
What JSON Schema version does this tool generate?
The tool generates schemas compliant with JSON Schema Draft-07 ($schema: http://json-schema.org/draft-07/schema#). Draft-07 is widely supported by validation libraries including Ajv, jsonschema (Python), and most API documentation tools.
How accurate is the type inference?
The tool infers types from the actual values in your JSON. It distinguishes between integers and floats, detects null values, and recursively analyzes nested objects and arrays. For best results, provide a complete sample with all fields populated.
Can I generate schemas for large JSON files?
Yes, the tool processes JSON in your browser without size limits. However, very large JSON structures (tens of thousands of lines) may cause slower performance. For typical API response schemas, performance is instant.