json schema to typescript interface converter
typetools
instant, client-side type converter • 0ms network latency
export interface RootPayload {
userId: string;
username: string;
email: string;
isActive: boolean;
score: number;
roles: string[];
}step-by-step integration guide
technical specification differences & end-to-end conversion workflow
Compiling JSON Schema Combinators into TypeScript Algebraic Types
While JSON Schema validates data structures at runtime using boolean set logic, TypeScript enforces structural typing at compile time using interfaces, intersection types (&), and union types (|). Translating a JSON Schema document into idiomatic TypeScript requires bridging several semantic differences. First, in JSON Schema, an object's properties are optional by default unless their property name is listed in the sibling required: [...] array; in TypeScript, interface properties are required by default unless suffixed with the ? optional modifier. Second, JSON Schema supports Boolean algebra combinators—allOf, anyOf, and oneOf—alongside local JSON Pointer references ($ref: "#/$defs/Address").
Resolving $defs, Required Sets, and AdditionalProperties
Our client-side JSON-Schema-to-TypeScript compiler parses the schema AST and resolves internal $defs and definitions pointers into standalone exported TypeScript interface and type declarations. For each object schema, the generator cross-references every key in properties against the required set: keys absent from required receive the ? optional flag. JSON Schema enum arrays are compiled into literal union types (e.g., "pending" | "active" | "archived"), allOf arrays are compiled into TypeScript intersection types (A & B), and anyOf/oneOf arrays are compiled into TypeScript union types (A | B). Furthermore, if additionalProperties: false is set, the interface is locked to known keys; otherwise, an index signature [k: string]: unknown; can be appended.
frequently asked questions
common developer questions answered
q:How are JSON Schema 'allOf', 'anyOf', and 'oneOf' keywords translated to TypeScript?
The compiler maps allOf to TypeScript intersection types (TypeA & TypeB), and maps anyOf and oneOf to TypeScript union types (TypeA | TypeB).
q:How does the converter handle internal '$ref' pointers to '#/$defs/' or '#/definitions/'?
All reusable schemas inside $defs or definitions are emitted as top-level named TypeScript interfaces, and any property using $ref is typed directly with that interface identifier.
q:What happens when 'additionalProperties' is set to false vs. a schema object?
When additionalProperties is false, only explicitly declared properties are emitted on the interface. When additionalProperties is a schema object, a typed index signature ([key: string]: ValueType) is generated.