The generated type looks wrong

The sample JSON probably is not representative. Include examples with optional fields, non-empty arrays, and nullable values so inference has enough signal.

An empty array became `any[]` or `unknown[]`

That's expected. An empty array contains no item information, so the tool has to fall back to a broad type.

A field should be optional but isn't

The generator only sees the pasted sample. If every object includes the field, it will infer a required property. Add samples where the field is missing, or edit the output manually.

A field became `string | number | null` and feels too broad

Your sample data contains multiple value shapes for that property. The union may be accurate, but if the API contract is stricter than the sample, narrow it by hand.

The tool says a property name is not supported

Rename the JSON key in your sample or reshape the sample before generating. Keys containing apostrophes or ending in `--?` cannot be emitted safely by the bundled generator.

Is this safe for private payloads?

Yes for local use in this app. The JSON to TS generation runs in the browser, so the data stays on your machine instead of being sent to a server.

JSON to TypeScript Interface Generator

Generate TypeScript interfaces or type aliases from a JSON sample, entirely in your browser.

Root type name

Generated as RootObject

Generation style

JSON input

Ctrl/Cmd+Enter

TypeScript output

Generated code appears here

Sample-based inference

Output reflects only the JSON object or non-empty array of objects sample you provide. Missing keys or alternate shapes will not be inferred.

Arrays and unions

Mixed object samples can merge into optional fields or unions. Root arrays must contain objects only.

Optional fields

Properties may become optional when sibling objects differ. Null handling and exact intent still need human review.