JSON → TypeScript Generator
Generate TypeScript interfaces from JSON data automatically
JSON Input
Frequently Asked Questions
How do I generate TypeScript interfaces from a JSON API response?
Paste the JSON object or array into the input field, set the root interface name (default Root), and click Generate TypeScript. The tool inspects each key and value, infers the TypeScript type (string, number, boolean, null, nested interface, or array), and outputs exportable interface declarations ready to drop into your TypeScript project.
Does the TypeScript generator work offline and without sending my data anywhere?
Yes. The entire generation runs in your browser with JavaScript. Your JSON data — which may contain internal field names, data structures, or proprietary API shapes — is never transmitted to any server. The output TypeScript is generated and displayed locally.
How does this tool handle nested JSON objects and arrays?
Nested objects generate a separate named interface. For example, a field called address containing city and zip becomes an Address interface, and the parent interface references it as address: Address. Arrays are typed as element-type arrays (e.g., string[] or Tag[]). Interface names are derived by PascalCasing the field name.
When should I use optional properties in the generated TypeScript interface?
Enable the ‘Optional props’ checkbox when some fields in the JSON may be absent on certain objects. This adds a ? after each property name (e.g., email?: string), making TypeScript accept objects that omit those fields. By default, all inferred properties are required. If you are modeling an API with optional query parameters or nullable fields, optional props prevents type errors.
What is a major limitation of inferring TypeScript types from a single JSON sample?
Like JSON Schema inference, the generator can only see what is present in the sample. A field that is sometimes string and sometimes number will be typed based on whichever value appears in the sample. Union types such as string | number | null are not automatically generated. Review the output carefully and add union types, generics, or more specific string literal types where your actual data varies.