FREE BROWSER TOOLDevelopment
JSON to TypeScript Type Generator
Turn an API response or AI-produced JSON into a TypeScript draft. The generator examines array items, combines object shapes and keeps nullable values visible. Paste representative records covering different response shapes.
Calculations run in your browser. No account or API key is needed.
Your result
- Inferred properties
- 7
export type ApiResponse = {
"items": {
"id": string;
"title": string;
"published": boolean;
"author": string | null;
"tags"?: string[];
}[];
"nextCursor": null;
};How to use this tool
Paste valid JSON and choose a type name.
Generate the declaration and inspect optional properties.
Compare it with your API contract before copying it into your project.
How sample inference works
Strings, numbers and booleans become broad primitive types. Missing fields across object samples become optional; explicit null remains a union member. Empty arrays use unknown[] because there is no evidence for their element type. Duplicate keys are rejected rather than silently discarded.
A draft for typed workflows
A generated declaration describes the examples you provided. It cannot discover undocumented fields, allowed enum values or every response variant. Add representative success and failure cases, review the result, and keep runtime validation where external data enters your application.
Common questions
Does this validate an API response?
No. The output is a TypeScript declaration, not a runtime validator or a JSON Schema.
Are dates and identifiers converted?
No. Date-looking strings stay string, and numeric values become number. No literal values are emitted. Conversion runs locally in your browser.