JSON Schema & type generator tools
When an API response needs a formal contract, or a growing codebase needs types instead of hand-written interfaces, these tools turn real JSON samples into something structured. Generate a JSON Schema to document and validate a payload, or skip straight to typed code in TypeScript, Go, Java, Python, Swift, Rust, C#, Dart or Scala without writing the models by hand.
The type generators look at multiple array samples together, not just one object, so optional and inconsistent fields get detected rather than guessed. JSON Schema Mock Data Generator produces fixtures from a seed so test data stays reproducible across runs, and JSON Schema diff flags breaking changes by direction — a field required for producers is a different risk than one required for consumers. All of it runs locally in your browser.
11 tools
Generate types and models
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JSON to TypeScript
Generate TypeScript types from multiple array samples with field analysis
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JSON to Go
Generate Go structs from all array samples with json tags and nil pointers
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JSON to Java
Generate Jackson models from JSON samples with nullable field detection
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JSON to Python
Build dataclass or Pydantic models from representative API responses
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JSON to Swift
Create Swift Codable structs from API examples with optional field inference
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JSON to model
Generate Rust, C#, Dart, PHP and Scala types from JSON samples
Build and validate JSON Schema
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JSON Schema generator
Infer JSON Schema from multiple samples with optional field detection
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JSON Schema validator
Check instances against schemas and report rule violations with paths
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JSON Schema diff
Compare schemas and flag breaking changes by data direction
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JSON Schema Mock Data Generator
Generate seeded JSON fixtures from JSON Schema with reproducible results
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XSD to JSON Schema
Map XSD elements and types to JSON Schema with approximation warnings
Schema & Type Generation tools FAQ
Paste one or more sample responses into JSON to TypeScript — using several array samples instead of one lets it notice fields that are sometimes missing and mark them optional instead of guessing. The same approach works for JSON to Go, JSON to Java, JSON to Python and the other JSON to model generators on this page.
A TypeScript interface only checks shape at compile time, in your codebase. A JSON Schema is a runtime, language-independent contract you can validate real payloads against with JSON Schema validator, share with other services, or generate mock test data from with JSON Schema Mock Data Generator.
Run both versions through JSON Schema diff. It reports changes by direction, since a newly required field breaks anyone producing data against the old schema, while a newly optional field mainly affects strict consumers. Reading the direction, not just the diff itself, is what tells you who actually breaks.