JSON to TypeScript Converter

TypeScript's promise is compile-time safety for JavaScript — but only if your data has types. When you consume a REST API, a config file, or a WebSocket payload, the response arrives as plain JSON with no type information. Hand-writing the matching interface is tedious and error-prone, especially as payloads grow. A JSON to TypeScript converter turns that sample into a precise, typed interface in seconds.

OpenToolLab's JSON to TypeScript converter infers the correct TypeScript type for every field. Strings become string, numbers become number, booleans become boolean, arrays become typed arrays like string[], and objects become their own exported interfaces. Fields that are null or missing in the sample are marked optional with ?, so the generated type matches what your code actually receives.

Nested objects are handled by generating a separate interface for each level, named from the parent property in PascalCase. A payload with a user object, a posts array, and tags arrays becomes a clean set of related interfaces — user, post, and the root interface that references them. This mirrors how you would structure the types by hand, minus the manual work.

The converter is part of a multi-language engine, so the same JSON can generate TypeScript, Dart, Kotlin, or Swift from one window. Paste your payload once, switch languages with a tab, and copy the output for the stack you are working on. This is a genuine time-saver when you maintain typed clients for more than one platform.

Privacy is built into the design. Type inference runs entirely in your browser — your API responses, config files, and schemas never leave your device. Open the DevTools Network tab while converting and you will see zero requests. There are no servers, no accounts, and no logs of your data.

Beyond code generation, the tool doubles as a way to learn TypeScript typing. Study how an optional field becomes ?, how an array of objects becomes Interface[], and how union types handle mixed arrays. The generated output is idiomatic TypeScript that matches how experienced teams structure their models.

Use it as part of a real workflow: fetch a sample from your API, convert it to an interface, then JSON.parse the real response with a cast to that interface. You get full autocomplete, refactor safety, and compile-time validation across your codebase. Whether you are building a Swagger-based client, typing a Redux slice, or modeling a config schema, this converter removes the typing bottleneck.

OpenToolLab is a completely free JSON to TypeScript converter with no signup and no limits. Paste, generate, and copy — privately and instantly, entirely in your browser.