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Guide
About the JSON to TypeScript Generator
When you consume an API, you usually have an example JSON response but no matching types. Writing TypeScript interfaces by hand is tedious and error-prone, especially for deeply nested payloads. This tool reads any JSON object and generates ready-to-use TypeScript interfaces that describe its shape — nested objects become their own interfaces, arrays are typed by their elements, and mixed values are inferred as unions.
Paste a sample response and get types you can drop straight into your codebase, giving you autocomplete and compile-time safety with none of the manual typing. Everything is processed locally.
How the shape is inferred
The generator walks your JSON and infers a type for every field: strings, numbers, and booleans map directly; nested objects are extracted into their own named interfaces; and arrays are typed by inspecting their elements. Because inference is based on a single example, it's a strong starting point — but you should still review fields that can be null, optional, or vary between responses.
Tips for better types
Feed the tool the most complete example you have — one where optional fields are present — so nothing is missed. After generating, mark fields that may be absent with ?, and widen types where the API can return more than the sample shows (for example a status string that could be one of several values). A representative sample yields interfaces you'll barely need to touch.
How to use it
- 1Paste a JSON object or API response into the input.
- 2The matching TypeScript interfaces are generated instantly.
- 3Rename the root interface to something meaningful for your domain.
- 4Copy the interfaces into your project and refine optional or union fields as needed.
Frequently asked questions
Does this handle nested objects and arrays?
Yes. Nested objects are extracted into their own interfaces and arrays are typed by their element type, so complex, deeply nested JSON is fully supported.
Will it detect optional fields?
It infers types from the example you provide. If a field is absent in your sample, it will not appear — so use a complete example and mark truly optional fields with "?" afterward.
Can it generate types instead of interfaces?
The output uses interfaces, which are ideal for object shapes. You can convert any of them to a type alias by hand if your style guide prefers types.
Is my JSON uploaded to a server?
No. Parsing and type generation run entirely in your browser, so even private API responses stay on your device.
What about fields that are sometimes null?
A single example cannot reveal that a field is nullable. Review the output and add "| null" or "?" where the API can omit or null a value.