Online JSON to TypeScript Interface Generator
Transform raw JSON payloads into clean, idiomatic TypeScript declarations. Nested objects are automatically extracted into distinct, reusable interfaces, array items are type-inferred with union support, and missing keys across array records are cleanly tagged with optional modifiers.
#How to Use This Tool
#Mathematical Formula & Standards
#Edge Cases & Technical Considerations
Heterogeneous Array Element Unions
When an array contains mixed types (e.g. [1, "hello", true]), the engine infers a consolidated union type: (string | number | boolean)[].
Special Characters and Reserved Identifier Keys
Property names containing hyphens, spaces, or leading digits (e.g. "x-api-key", "123code") are automatically wrapped in quotes to produce syntactically valid TypeScript.
Optional Field Detection Across Array Records
When parsing an array of objects where certain keys appear only in a subset of items, the engine automatically flags those properties as optional (key?: type).
#Frequently Asked Questions
Q:Does my JSON data get uploaded to an external server?
No. The AST parser and TypeScript generator run 100% locally inside a dedicated Web Worker in your browser. When using URL sharing, the state is compressed into the URL hash fragment (#v=1&d=...), which per HTTP specifications is never sent to web servers or logged.
Q:What is the difference between interface and type alias output?
Interfaces in TypeScript support declaration merging and are standard for object contracts. Type aliases allow union and tuple definitions. Both provide identical compile-time type safety in modern TypeScript projects.
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