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JSON to TypeScript

JSON to TypeScript converts JSON samples into TypeScript interfaces and type aliases, with inferred optional fields, unions, and array item structure for API modeling, frontend bootstrapping, and mock data cleanup.

JSON

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TypeScript
JSON to TypeScript

Quick Start

1
Paste a valid JSON sample into the left editor.
2
Optional: set a custom root type name such as ApiResponse before generation.
3
Review the generated declarations on the right. Object roots become interface declarations; array and primitive roots become type aliases.
4
Use Copy or Download to reuse the generated .ts output in your project.

Common Scenarios

Turn real API responses into TypeScript types you can use immediately in frontend pages, SDK clients, or integration tests.

Before formalizing an API contract, inspect how optional fields, null values, and union types are inferred from real JSON samples.

Convert mock JSON data into quick type definitions for fixtures, Storybook stories, or prototypes.

When backend payloads change, use the latest JSON sample to review whether nested declarations like User or Meta also need updates.

Usage Advice

Use a representative JSON sample. The generator only infers from the values you paste, so missing cases will not appear in the output.
Empty arrays become unknown[], and empty objects become interfaces extending Record<string, unknown> until you provide richer sample data.
Nested declarations are normalized from property names, so newer output prefers names like User or Meta instead of older root-prefixed forms.
Generation only runs on valid JSON. Fix syntax errors first; the editor shows line and column details when parsing fails.
Valid custom root names are preserved as-is, while invalid names are normalized to a legal PascalCase TypeScript identifier.

Limitations & Compatibility

This tool infers types from sample data, not from a formal schema. Fields missing from your sample cannot be guessed.
Input must be strict JSON. Comments, trailing commas, and other JavaScript-only syntax are rejected.
Generated output does not include export statements. Add them yourself if your project requires exported declarations.
The result is static TypeScript code only. It does not create runtime validators, parsers, or serializers.

Privacy & Security

All processing happens locally in your browser. You can replace the JSON sample and regenerate results at any time before copying or downloading.

FAQ

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Continue with these related tools for the next step.