How to use this tool
- Paste a representative JSON object or array of objects.
- Choose a root interface name that matches your API or model.
- Generate interfaces, copy the result, and review optional fields before using it in code.
Developer Utility
JSON to TypeScript Interface
Infer TypeScript interfaces from JSON samples without uploading payloads. Use it for API response types, test fixtures, documentation examples, and quick frontend model drafts.
Waiting for JSON input.
Real examples
Sample input/output: a JSON array with user.name, user.role, and missing active fields becomes nested interfaces with optional properties where the sample is inconsistent.
Common use cases
Use it for API response typing, fixture modeling, mock data cleanup, migration notes, frontend props drafts, and quick checks before writing a stricter runtime schema.
Related workflow
Validate sample JSON in JSON Formatter, compare versions in JSON Diff, then generate TypeScript here and escape code snippets with JSON Escape / Unescape.
Common errors and fixes
| Error | Meaning | Fix |
|---|---|---|
| Invalid JSON | The browser parser cannot read the sample. | Format or validate it in JSON Formatter first. |
| Mixed array values | The same array contains different primitive or object shapes. | The output uses union types where possible. |
| Missing fields in arrays | Some objects do not include a key. | The property is marked optional with ?. |
Edge cases table
| Case | Generated type |
|---|---|
| Null value | null is included in the union when a field is nullable. |
| Invalid property name | The property is emitted as a quoted key. |
| Empty array | The field becomes unknown[] because no element shape exists. |
JSON to TypeScript FAQ
Does this upload JSON?
No. The sample is parsed locally in your browser.
Are the generated types guaranteed?
No. They reflect the sample you paste. Review them before using them in production code.
Can it handle arrays?
Yes. Arrays of objects are merged so missing keys become optional and nested objects produce extra interfaces.
Should I still use validation?
Yes. TypeScript types help at compile time; runtime data still needs validation when trust matters.