Documenting APIs
Paste API responses to generate TypeScript definitions for SDKs or internal documentation.
JSON → TypeScript
Infer a TypeScript interface from a JSON object.
Result
Overview
Turn sample JSON payloads into a quick TypeScript starting point. Perfect for wiring new API clients or sharing data contracts with teammates.
Use Cases
Rapid prototyping
Infer types while experimenting in a playground without manually writing interfaces from scratch.
Onboarding teammates
Share generated interfaces to explain object structures when ramping up new developers.
How to Use
Paste valid JSON
Provide a representative sample object. Arrays will derive their element type from the first item.
Set an interface name
Adjust the interface name to match your domain model. Optional fields are always included in the result.
Refine manually
Use the generated interface as a baseline and refine complex unions or nested shapes by hand.
Frequently Asked Questions
Does the tool detect optional properties?
Optionality is not inferred automatically. Every observed property is required so you can decide manually which ones should be optional.
How are arrays handled?
The first element determines the inferred type. Empty arrays default to `unknown[]` so you can refine them afterwards.
Related Tools
Concept Notes
Inferring types from imperfect samples
Type inference mirrors the data you provide: keys absent in some objects become optional, and mixed-type arrays widen to unions. Clean, representative samples yield cleaner interfaces; otherwise, post-editing the generated types or normalising data first prevents accidental any usage and keeps downstream API contracts tight.