Free JSON to TypeScript generator
Paste API or config JSON and generate TypeScript interfaces instantly. Nested objects become named interfaces; uneven array objects mark missing keys as optional. Runs entirely in your browser.
How to use this tool
- 1
Open JSON to TypeScript
Generate interfaces from sample API JSON.
- 2
Paste JSON and set root name
Choose the root type name and whether to export interfaces.
- 3
Copy TypeScript
Copy the generated types into your project.
Quick facts
| Runs locally? | Yes — inference runs only in your browser. |
|---|---|
| Is anything uploaded? | No. JSON stays in this tab. |
| Optional properties? | When array objects omit keys, those properties are marked optional. |
| Pair with JSON formatter? | Use the JSON formatter first if your payload is minified on one line. |
Top use cases
- Infer TypeScript interfaces from JSON, nested types, optional keys, export toggle — local only.
- Runs locally?: Yes — inference runs only in your browser.
- Is anything uploaded?: No. JSON stays in this tab.
- Optional properties?: When array objects omit keys, those properties are marked optional.
- Pair with JSON formatter?: Use the JSON formatter first if your payload is minified on one line.
FAQ
Does it emit classes?▾
No — only interfaces and type aliases, ready to paste into .ts files.
Union types?▾
Mixed value types in the same field become union types (for example string | number).
Empty arrays?▾
They infer as unknown[] until you add a sample element.
JSON with null?▾
null becomes the null literal type in unions where needed.
Strict accuracy?▾
Output is best-effort from samples — review before production APIs.
Large JSON files?▾
Very large payloads may slow the tab; split or trim for huge trees.