JSON to TypeScript Interface

JSON to TypeScript Interface

Instantly convert any JSON object into clean TypeScript interfaces. Free online tool — supports nested objects, arrays, and optional fields. No install needed.

Updated April 2026

Root Interface Name
Output
1
TypeScript Interface

// Paste JSON on the left // to generate TypeScript interfaces

Shift + Enter to Copy

JSON to TypeScript Interface Generator — Free Online Tool

Stop writing TypeScript interfaces by hand. Paste any JSON object — an API response, a config file, a database record — and get production-ready TypeScript interfaces in milliseconds. No installation, no account, no limits.

This free online converter handles the full range of real-world JSON structures: nested objects, mixed arrays, null values, and string/number/boolean fields. The output is compatible with TypeScript 3.0 and above, and works in any modern TypeScript, React, Next.js, Vue, or Angular project.

How to Use the JSON to TypeScript Converter

Converting JSON to TypeScript interfaces takes three steps:

  1. Paste your JSON — Copy any valid JSON object or array into the input panel on the left.
  2. Set the root interface name — The top field defaults to RootObject. Rename it to match your domain model (e.g., User, ApiResponse, Product).
  3. Copy the result — Click Copy or press Shift+Enter to grab the generated interfaces and paste directly into your .ts or .tsx files.

Switch between interface and type output using the toggle at the top — both formats are fully interchangeable in TypeScript.

How TypeScript Interfaces Are Generated from JSON

The generator analyses each field in your JSON and maps it to the appropriate TypeScript type:

  • Strings → string
  • Numbers → number
  • Booleans → boolean
  • Null values → null
  • Arrays of strings/numbers → string[], number[]
  • Arrays of objects → a named interface with [] suffix
  • Nested objects → a separate named interface, referenced by the parent

For deeply nested structures, the tool generates one interface per object level and orders them so that referenced types always appear before they are used. The root interface comes last — the standard convention in TypeScript files.

Common Use Cases for JSON to TypeScript Conversion

  • Typing REST API responses: Paste the JSON returned by your backend and instantly get typed interfaces to use in your frontend fetch/axios calls.
  • Typing configuration files: Convert config.json or appsettings.json to a typed interface so your IDE can autocomplete configuration keys.
  • Accelerating development: Skip the boilerplate of writing interfaces manually for complex nested payloads.
  • Onboarding new data sources: When integrating a third-party API, paste a sample response to understand its shape and generate starter types immediately.
  • Prototyping: Get typed scaffolding in place quickly before writing business logic.

Frequently Asked Questions

How to convert nested JSON to TypeScript interface?

Paste your nested JSON directly into the input field. The generator handles nested objects recursively — each nested object gets its own named interface. For example, if your JSON has a profile field containing an object, the tool generates both a RootObject interface (with profile: Profile) and a separate Profile interface for the nested structure. Interfaces are ordered so dependencies appear first.

Can I convert a JSON API response to TypeScript?

Yes. Copy the raw JSON from your browser's network tab, Postman, or any API testing tool, paste it into the left panel, and the converter generates all the TypeScript interfaces you need. This is especially useful when consuming REST APIs where the shape of the response is defined by the backend.

How are JSON arrays handled in TypeScript generation?

Arrays of primitive values (strings, numbers, booleans) are typed as string[], number[], or boolean[]. Arrays of objects generate a named interface for the element shape and return InterfaceName[]. Arrays containing mixed types are typed using a union like (string | number)[]. Empty arrays default to unknown[] since the element type cannot be inferred.

What is the difference between interface and type output?

Both interface and type declarations describe object shapes in TypeScript and are mostly interchangeable. Interfaces support extends and declaration merging, which makes them the conventional choice for public APIs and library definitions. Type aliases (type) support union and intersection types more naturally. The toggle in the tool lets you choose whichever format fits your project's conventions.

Does it handle null values in JSON?

Fields set to null in the JSON are typed as null in the generated TypeScript. In a real project you would typically widen these to string | null or number | null depending on what the field can actually hold. The generator gives you the safest accurate type based on the sample data you provide.

Resources

Related Tools