JSON to TypeScript

Generate TypeScript interfaces from JSON

JSON Input

TypeScript Interfaces

How to use JSON to TypeScript

  1. •Paste your JSON into the input panel on the left. This can be a sample API response, a configuration object, or any valid JSON structure.
  2. •Review the generated interfaces that appear in the output panel. The tool automatically infers types from values: strings, numbers, booleans, arrays, and nested objects all get proper TypeScript types.
  3. •Adjust naming if needed. The root interface is typically named RootObject by default. Rename it to match your domain (e.g., User, ApiResponse).
  4. •Copy the output and paste it into your .ts or .d.ts file.

What are TypeScript interfaces?

TypeScript interfaces define the shape of an object at compile time. They tell the TypeScript compiler (and your IDE) exactly which properties an object has, what types those properties are, and whether they are required or optional. When you write interface User { name: string; age: number }, you create a contract that any object claiming to be a User must satisfy.

Interfaces are erased at runtime — they produce zero JavaScript output. Their purpose is purely for static analysis: catching typos, preventing you from accessing properties that do not exist, and enabling autocomplete in your editor. This makes them a zero-cost abstraction that dramatically improves developer experience.

When working with external APIs, you often receive JSON responses that TypeScript knows nothing about. Manually writing interfaces for deeply nested responses is tedious and error-prone. That is exactly where this tool helps: it inspects the actual data and generates accurate interfaces, including nested types, arrays of objects, and union types where appropriate.

Common use cases

  • •API integration: You hit a REST API, copy the JSON response, and generate interfaces so that the rest of your codebase is fully typed against the real data shape.
  • •Configuration files: Your app reads a JSON config at startup. Generating an interface ensures you access only valid config keys with the right types.
  • •Database seeding: When writing seed data as JSON, generating interfaces first helps catch malformed records before they hit the database.
  • •Documentation: Generated interfaces serve as living documentation of your data model that stays in sync with real payloads.

FAQ

Q: Does it handle optional fields? A: If you paste a single JSON object, every field is treated as required. To get optional fields, paste an array of objects where some objects omit certain keys — the tool will mark those keys as optional with ?.

Q: What about arrays with mixed types? A: The tool creates a union type. For example, an array containing both strings and numbers becomes (string | number)[].

Q: Can I use this for JSON from a GraphQL response? A: Absolutely. The tool does not care where the JSON comes from. Paste the data portion of a GraphQL response and you get accurate interfaces.

Is my data safe?

Yes. This tool runs entirely in your browser. Your data is never sent to our servers.

How to use JSON to TypeScript

  1. Paste your JSON into the input panel on the left. This can be a sample API response, a configuration object, or any valid JSON structure.
  2. Review the generated interfaces that appear in the output panel. The tool automatically infers types from values: strings, numbers, booleans, arrays, and nested objects all get proper TypeScript types.
  3. Adjust naming if needed. The root interface is typically named RootObject by default. Rename it to match your domain (e.g., User, ApiResponse).
  4. Copy the output and paste it into your .ts or .d.ts file.

What are TypeScript interfaces?

TypeScript interfaces define the shape of an object at compile time. They tell the TypeScript compiler (and your IDE) exactly which properties an object has, what types those properties are, and whether they are required or optional. When you write interface User { name: string; age: number }, you create a contract that any object claiming to be a User must satisfy.

Interfaces are erased at runtime — they produce zero JavaScript output. Their purpose is purely for static analysis: catching typos, preventing you from accessing properties that do not exist, and enabling autocomplete in your editor. This makes them a zero-cost abstraction that dramatically improves developer experience.

When working with external APIs, you often receive JSON responses that TypeScript knows nothing about. Manually writing interfaces for deeply nested responses is tedious and error-prone. That is exactly where this tool helps: it inspects the actual data and generates accurate interfaces, including nested types, arrays of objects, and union types where appropriate.

Common use cases

  • API integration: You hit a REST API, copy the JSON response, and generate interfaces so that the rest of your codebase is fully typed against the real data shape.
  • Configuration files: Your app reads a JSON config at startup. Generating an interface ensures you access only valid config keys with the right types.
  • Database seeding: When writing seed data as JSON, generating interfaces first helps catch malformed records before they hit the database.
  • Documentation: Generated interfaces serve as living documentation of your data model that stays in sync with real payloads.

FAQ

Q: Does it handle optional fields? A: If you paste a single JSON object, every field is treated as required. To get optional fields, paste an array of objects where some objects omit certain keys — the tool will mark those keys as optional with ?.

Q: What about arrays with mixed types? A: The tool creates a union type. For example, an array containing both strings and numbers becomes (string | number)[].

Q: Can I use this for JSON from a GraphQL response? A: Absolutely. The tool does not care where the JSON comes from. Paste the data portion of a GraphQL response and you get accurate interfaces.

Is my data safe?

Yes. This tool runs entirely in your browser. Your data is never sent to our servers.