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JSON to TypeScript Generator

Generate readable TypeScript declarations from an example payload, then compare them with the real API contract. Choose interface or type output, nested declarations, optional fields and code style.

Direct answer

A JSON-to-TypeScript generator infers compile-time declarations from observed values. These declarations improve editor and build-time checks, but they do not validate data at runtime.

Generate the declarations, review the inferred edge cases and add runtime validation where needed.

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Input JSON

Example JSON loaded.
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Output TypeScript

1export interface Root {2  user: User;3}4 5export interface Address {6  city: string;7  zip: string;8}9 10export interface Profile {11  age: number;12  address: Address;13}14 15export interface User {16  id: number;17  name: string;18  email: string;19  isActive: boolean;20  roles: string[];21  profile: Profile;22  lastLogin: string;23}24

How to use it

  1. Paste/upload JSON or fetch a supported public sample.
  2. Set the root name, interface/type style, optional fields, array syntax, nested extraction, readonly/export and semicolon preferences.
  3. Review missing unions/nulls/optional cases, then copy or download the .ts output.

Key features and settings

  • Interface or type-alias output.
  • Optional-field and array-style controls.
  • Extracted nested declarations plus readonly/export options.
  • unknown-over-any preference and optional string-literal unions.

Supported input and output

Input: JSON text or file, a supported public URL. Output: .ts.

Use cases

  • Create frontend models from an API example.
  • Document nested response shapes during integration.
  • Compare static types with a Zod schema when runtime validation is also needed.

Which workflow should you choose?

Use JSON to TypeScript Generator for: Interface or type-alias output. Use JSON to Zod Schema Generator for: Configurable schema name and output style.

Privacy and data path

In the current implementation, pasted/uploaded content is processed in the browser, while “Extract from URL” uses a server-side proxy to fetch the source.

Limits and troubleshooting

  • One payload cannot reveal every optional field or union branch.
  • Use JSON to Zod or another runtime validator when untrusted data must be checked after parsing.
  • There is no universal size promise; large-input performance depends on browser memory and device capability.

FAQ

Do TypeScript types validate JSON at runtime?

No. TypeScript types are erased at runtime. Use a runtime schema such as Zod when the application must reject invalid payloads.

Is my data uploaded to a server?

In the current implementation, pasted/uploaded content is processed in the browser, while “Extract from URL” uses a server-side proxy to fetch the source.

What are the file or data limits?

There is no universal size promise; large-input performance depends on browser memory and device capability.

Does it work on mobile?

The page is web-based and may work in a modern mobile browser, but file-picker behavior, memory and cross-device compatibility are not verified for every device. Use a desktop browser for large or complex inputs.

Which workflow should you choose?

Use JSON to TypeScript Generator for: Interface or type-alias output. Use JSON to Zod Schema Generator for: Configurable schema name and output style.

Related tools

JSON to Zod Schema GeneratorGenerate a starting point for runtime validation in TypeScript.JSON to JSON Schema GeneratorGenerate standalone JSON Schema with explicit dialect control.JSON Formatter OnlineFormat and validate JSON before conversion, or inspect the result afterward.

Generate the declarations, review the inferred edge cases and add runtime validation where needed.