JSON → TypeScript interfaces

Client

Paste a JSON object or array to emit export interface declarations aligned with the sample—handy for typing API responses before you wire fetch or JSON.parse.

Learn more: JSON and TypeScript

Paste a sample JSON object or array to generate TypeScript interfaces that mirror its shape—a starting point for typing parsed data or REST payloads.

Interfaces vs runtime data

TypeScript types describe the expected form of values at compile time; JSON from the network is still untyped at runtime until you validate or narrow it. Generated interfaces capture field names and nesting from one example so you can annotate `JSON.parse` results or generic helpers.

From sample to types

One response does not prove every future payload matches, but it documents keys and structure for a first draft. You may add optional properties, unions, branded types, or stricter number literals once you know your API contract.

Scope

Like the C# and Java generators on this hub, this flow is JSON → TypeScript scaffolding only. It does not read existing `.ts` files or produce runtime validators—pair with your team’s schema or test strategy when correctness matters.

JSON → TypeScript

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Parses JSON in your browser and emits classes inferred from the sample shape. Nested objects become nested types; arrays use the first element only to guess item shape. Nothing is uploaded.

Property names use camelCase when safe; adjust unions, optional fields, and readonly to match your API contract.

Common use cases

  • Bootstrap interfaces for fetch() responses while exploring a new HTTP API.
  • Turn example config JSON into typed shapes before moving settings into typed modules.
  • Share readable type scaffolding in docs or PRs when the payload is stable enough to sample.

Common mistakes to avoid

  • Treating one response as the full contract

    Optional fields, unions, and discriminated variants appear only when samples include them—merge multiple examples or use JSON Schema when strictness matters.

  • Shipping generated names without review

    Rename interfaces and properties to match your codebase conventions; generated labels are a starting point.

FAQ

Is TypeScript generated on your servers?

No. Inference runs locally from the JSON you paste.

Should this replace OpenAPI or JSON Schema tooling?

Use it for quick drafts. For published APIs, prefer schema-first sources that encode optionality and validation rules explicitly.

More tools

Related utilities you can open in another tab—mostly client-side.