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JSON to TypeScript Interface

Generate deterministic TypeScript Interfaces or Types from a JSON object structure.

What is the JSON to TypeScript Interface?

The JSON to TypeScript Interface tool converts any JSON object or array into TypeScript interface definitions with inferred types. Paste your JSON, give the root interface a name, and it generates ready-to-use type declarations.

It infers primitive types (string, number, boolean), array element types, and nested objects, generating a separate named interface for each nested structure so the output stays readable and reusable.

The tool is free and runs entirely in the browser using the json-to-ts library. There is no signup and your JSON is never sent to a server, so it is safe to use with internal API responses.

How to use the JSON to TypeScript Interface

  1. 1Set the Interface Name field to the name you want for the root type, using PascalCase such as User or ApiResponse.
  2. 2Paste or type your JSON into the JSON Input box.
  3. 3Click Generate TypeScript Interface, or press Ctrl+Enter, to produce the type definitions.
  4. 4Review the generated interfaces in the TypeScript Output panel; nested objects become their own named interfaces.
  5. 5Click Copy to put the result on your clipboard, then paste it into your project.
  6. 6Press Ctrl+L to reset the input and start over, or pick a built-in example like User Object or Product.

What you can use it for

  • Turning a sample API response into typed interfaces for a frontend service layer.
  • Bootstrapping types for a third-party JSON payload you do not control.
  • Creating fixture types for unit tests from real JSON data.
  • Migrating a JavaScript codebase to TypeScript by deriving types from existing objects.
  • Quickly typing a configuration file or environment manifest stored as JSON.
  • Generating nested interfaces for deeply structured JSON without writing them by hand.

Key features

  • Automatic type inference for strings, numbers, booleans, arrays, and objects.
  • Separate named interfaces generated for each nested object.
  • Custom root interface name with built-in example payloads to start from.
  • Keyboard shortcuts: Ctrl+Enter to generate and Ctrl+L to clear.
  • One-click copy of the full TypeScript output.

Frequently asked questions

How do I convert JSON to a TypeScript interface?

Paste your JSON into the input box, enter a name for the root interface, and click Generate TypeScript Interface. The tool parses the JSON and produces interface definitions with inferred types that you can copy into your project.

Does the tool handle nested JSON objects?

Yes. Each nested object in the JSON becomes its own named TypeScript interface, and the parent interface references it by name. This keeps the generated output organized and reusable.

How are arrays typed in the generated interface?

Array properties are typed by their element type, for example string[] or number[]. Arrays of objects produce a dedicated interface for the element shape, which the array property then references.

What happens if my JSON is invalid?

If the input cannot be parsed, the tool shows an error message saying the JSON is invalid and does not produce output. Fix the syntax, such as a missing comma or unquoted key, and generate again.

Is my JSON sent to a server?

No. The conversion runs entirely in your browser using the json-to-ts library. Nothing you paste is uploaded, so it is safe to use with private or internal API data.

Can it tell the difference between optional and required properties?

The tool infers types from the single JSON sample you provide, so every key present in that sample is treated as required. If a property can be absent, add the optional marker (?) to it manually after copying the output.

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