JSON to TypeScript

Turn JSON into TypeScript Interfaces

Paste any JSON — an API response, a config file, a database row — and get accurate TypeScript interfaces you can drop straight into your editor. The tool walks the whole structure, names nested objects, collapses arrays of objects into a single reusable type, and marks a field optional when it is missing or null across the samples you paste. You name the root type, choose interfaces or type aliases, and copy or download a ready-to-use .ts file.

Unlike the web generators that POST your data to a server, this one runs entirely in your browser. That matters when the JSON you are typing types for is a real API payload with customer records, tokens, or internal field names — none of it leaves your machine. There is nothing to sign up for and no request is ever made.

One honest caveat: types are inferred from the exact JSON you paste, so they are only as complete as your sample. A field that is always null in your example becomes the null type, not string | null, and a key that never appears cannot be guessed. Paste a representative example (or an array with a few varied objects) and use the "All optional" option when you want a forgiving shape to tighten by hand.

Common Use Cases

• Type an API response: Drop a sample payload from a REST or GraphQL endpoint and get the interfaces to type your fetch results instead of reaching for any.
• Model config and fixtures: Turn a JSON config file, seed data, or test fixture into a matching interface so the shape stays honest as it grows.
• Nested and repeated objects: Deeply nested JSON and arrays of similar objects each get their own named, reusable type automatically.
• Loosen or tighten fields: Switch between inferring optionality from the data, forcing every field optional, or forcing every field required in one click.
• interface or type alias: Emit classic interface blocks, or type X = { … } aliases when your codebase prefers them — with an optional export on each.
• Debug a parse error: Malformed JSON is reported with the exact line and column so you can find the stray comma or missing quote fast.

Privacy: Parsing and type generation run entirely in your browser with client-side JavaScript. Your JSON is never uploaded, logged, or sent anywhere, and there is nothing to sign up for.