JSON to TypeScript Interface Online — Free Tool
Convert raw JSON payloads into strongly-typed TypeScript interfaces to accelerate development.
Privacy note: All processing happens entirely in your browser. No data is sent to our servers.
About this tool
TypeScript interfaces describe the shape of JSON from APIs. Paste a sample response and get typed interfaces with optional properties inferred from nulls and missing keys.
Accelerates front-end integration when OpenAPI specs are missing or outdated.
Common use cases
- Typing fetch responses in React or Angular apps
- Scaffolding models from Postman examples
- Documenting sample payloads in repos
- Migrating JavaScript projects to TypeScript
How to use
- Paste representative JSON (array or object) into the input.
- Review generated interfaces with nested types.
- Copy output into a .ts file in your project.
- Refine optional fields and rename root types to match your domain.
This page is available at /tools/json-to-typescript-interface/.
Understanding the result
- Union types may appear when array items differ in shape—normalize API or split interfaces.
- Optional properties (?) often mark keys absent in some samples or explicit nulls.
- Date strings stay as string unless you post-process to Date types.
- Regenerate when API schema changes—generated types are not a live contract.
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FAQ
Interface vs type alias?
Generator usually emits interfaces. Either works; teams pick one style guide.
How are nested arrays handled?
Arrays of objects become TypeName[] with nested interfaces for object items.
Can I use this for JSON Schema?
Output is TypeScript, not JSON Schema. Use schema tools if you need validation files.
What if JSON is invalid?
Fix syntax errors first. Trailing commas and single quotes must be corrected.