JSON to TypeScript

Paste your JSON into the left panel and the TypeScript interface appears instantly on the right. Every key becomes a typed property, nested objects become separate named interfaces, and arrays of objects generate array types like Variant[]. You can customise the root interface name and choose between interface and type output.

Both describe the shape of an object. interface supports declaration merging and is preferred by most style guides for object shapes. type is more flexible — it can represent unions, intersections, and primitives. For objects derived from JSON, either works; the "Both" option exports both so you can choose later.

Each nested object becomes a separate exported interface named after its key in PascalCase. For example, a key shippingAddress becomes interface ShippingAddress, and the parent interface references it by name. This prevents deeply inlined types and encourages reuse.

When enabled, any field whose JSON value is null gets the optional modifier ? in the interface. This signals that the field may not always be present or may be null, which is common in API responses where optional fields are omitted or set to null.

Arrays of a single object shape become ClassName[] where the class name is singularized from the key. Arrays of uniform primitives become string[], number[], etc. Mixed arrays become union arrays like (string | number)[] and fully heterogeneous arrays become unknown[].

The output is valid TypeScript that you can copy directly into your project. For production use, review fields that resolved to null or unknown — these occur when the JSON value was null or an empty array, so the generator couldn't infer the intended type. Replace them with your intended types manually.