How to use JSON to TypeScript
A real JSON response is a useful starting point for TypeScript types because it exposes nested objects, arrays and primitive values. The generator builds readable interfaces from the supplied sample and uses unions when array members have different observed shapes.
Generated declarations describe only the evidence in that sample. Fields absent from the sample cannot be discovered, and a null value does not reveal the non-null type it may hold later.
A reliable workflow
- Paste a representative JSON response with realistic optional and nullable cases
- Generate the interfaces and inspect nested names and unions
- Adjust domain names and optional fields before adding the types to a project
Worked example
Generate declarations from the included user profile sample
{"id":42,"name":"Nova","active":true,"roles":["admin","editor"],"profile":{"avatar":null,"score":9.4}}The result separates the nested profile shape, keeps roles as a string array and records avatar as null because the single sample provides no evidence of another value type
When this tool helps
- Bootstrap types for an unfamiliar API
- Document fixture shapes during frontend integration
- Spot inconsistent values inside mixed arrays
Accuracy and safety notes
- TypeScript types disappear at runtime and do not validate network data
- Use multiple representative samples or an authoritative API schema for production contracts
Frequently asked questions
Does XXF upload or store my data?+
No. The conversion runs locally in your browser. Your input is not sent to XXF, stored on a server or used for training.
How are arrays inferred?+
XXF inspects every sample item and combines distinct shapes into a safe union when necessary.