JSON to TypeScript Interface
This tool instantly converts any JSON object into well-structured TypeScript interfaces by recursively inspecting each key-value pair and mapping JSON data types to their TypeScript equivalents — strings, numbers, booleans, null, typed arrays, and nested interface definitions. Deeply nested objects automatically generate separate, named interfaces so your code stays readable and maintainable.
Type inference works entirely in your browser without sending data to any server, making it safe for use with sensitive payloads. Paste the raw JSON response from any REST API, configuration file, or database record, give the root interface a meaningful name, and receive clean, copy-ready TypeScript code in milliseconds.
How it works
For each JSON value: string → string, number → number, boolean → boolean, null → null, [] → unknown[] (or T[] when all items share type T), {} → a named interface. Nested objects recurse depth-first, emitting child interfaces before their parent so declarations are always in dependency order.
Use cases
- Typing REST API responses to enable IntelliSense and catch runtime shape mismatches
- Bootstrapping TypeScript models from JSON database documents or schema samples
- Converting third-party webhook payloads into typed contracts for safer integration
- Speeding up onboarding by auto-generating interfaces from example JSON fixtures
- Auditing deeply nested configuration files to understand their full type structure
Frequently asked questions
How do I convert JSON to a TypeScript interface?
Paste your JSON object into the tool, give the root interface a name, and it generates the matching TypeScript interfaces instantly. Each key-value pair is inspected recursively and mapped to a TypeScript type. You can then copy the output directly into your project.
Is my JSON data sent to a server?
No. Type inference runs entirely in your browser, so the JSON you paste never leaves your device. This makes the tool safe to use with sensitive API responses, configuration files, or database records.
How are arrays typed when converting JSON to TypeScript?
An empty array becomes unknown[], while an array whose items all share a type T becomes T[]. For arrays of objects, the tool generates a named interface for the element shape and types the array as that interface followed by []. Mixed-type arrays fall back to a union or unknown.
How does the tool handle nested objects?
Deeply nested objects are recursed depth-first, and each nested object generates its own separate, named interface rather than a large inline type. Child interfaces are emitted before their parents so declarations stay in dependency order and the code remains readable.
What TypeScript type does JSON null become?
A JSON null value maps to the TypeScript type null. Because JSON has no undefined, keys that are absent from the sample simply won't appear in the generated interface. If a field can be missing, you may want to mark it optional with a question mark after generating the code.