JSON to TypeScript
Generate TypeScript interfaces from any JSON. Nested objects, arrays, and optional fields inferred automatically.
About JSON to TypeScript
Paste a JSON object or array and instantly get matching TypeScript interfaces. Nested objects become their own named interfaces, arrays are typed by their element shape, and null values are marked optional. Perfect for typing API responses without writing types by hand. Runs entirely in your browser.
All processing happens entirely in your browser using modern web APIs. Nothing is uploaded to our servers — your data stays local and private. Free to use forever.
Common use cases
- Generating TypeScript types for an untyped third-party API response
- Bootstrapping interfaces from a sample JSON payload
- Typing configuration files and fixtures
- Converting a JSON schema sample into editor-friendly types
- Speeding up migration of a JavaScript codebase to TypeScript
How it works
The JSON is parsed and walked recursively to build a structural type tree. Each object becomes a named interface (named after its key, PascalCased); arrays are merged across all elements so an array of objects produces a single interface with optional fields where keys are missing; numbers infer to number, booleans to boolean, and null marks the field optional. The interfaces are emitted in declaration order with the root first.