JSON to TS Transformer
Hand-writing interfaces for a sample payload is slow and easy to get wrong on optional fields. Paste JSON and generate TypeScript types from that example. The result matches the sample, not every value the API might send later. Treat optional fields and union types as a starting point you still review.
How to use the JSON to TS Transformer
- Paste a representative sample. Include fields you expect to be present. A sample that omits a key will omit it from the type.
- Generate interfaces. Nested objects become named or inline types. Arrays use the element type found in the sample.
- Tighten the types. Replace string dates with a branded string or Date if that is your convention, and mark fields optional when the API sometimes drops them.
When it helps
- A new endpoint. Turn the example in the API docs into an interface before you write the client.
- Fixture-driven tests. Generate a type from the fixture so the test fails when someone changes the shape.
Common questions
Will one sample capture every field?
No. If a field is missing or null in the sample, the type will not know the real union. Generate from the richest example you have, then edit.
Are the types validated at runtime?
No. TypeScript types disappear at build time. Add a parser such as zod if you need to reject bad responses.
How are arrays of mixed objects handled?
The generator infers from the elements it sees. Mixed shapes may become a union or a widened object. Read that part carefully.
Does it upload my schema sample?
No. Conversion runs locally.
Read the guide: JSON to TypeScript Interface Generator: Stop Writing Types by Hand