TypeScript to JSON Schema

Convert TypeScript types to JSON Schema in your browser

Paste a TypeScript interface, type alias, enum, or a bare object type and get a pretty-printed JSON Schema. The converter is built for common API and form-validation models: primitives, arrays, tuples, optional properties, string/number literal unions, nested objects, local type references, extends, object intersections, index signatures, Record<string, T>, and JSDoc descriptions/constraints.

Everything runs locally in WebAssembly. Your source types are not uploaded, and the output is plain JSON you can copy into validators, OpenAPI schemas, tests, or documentation.

Worked example

Input:

/** A user visible in the admin UI. */
interface User {
  id: number;
  email: string;
  role: "admin" | "editor" | "viewer";
  bio?: string;
}

With Root type set to User, Schema draft set to 2020-12, Mark non-optional members required on, and Allow extra properties off, the result is an object schema with id, email, role, and bio under properties, role as a string enum, required: ["id", "email", "role"], additionalProperties: false, and the JSDoc sentence as the schema description.

Controls

• TypeScript source — paste declarations in one file. A bare type literal such as { id: string; tags?: string[] } also works.
• Root type — choose which declaration becomes the top-level schema. Leave blank to use the first declaration.
• Schema draft — emit Draft 2020-12 ($defs, prefixItems) or Draft-07 (definitions, tuple items array).
• Mark non-optional members required — when enabled, properties without ? or | undefined are listed in required.
• Allow extra properties — when disabled, object schemas get additionalProperties: false; index signatures and Record<string, T> still emit their value schema.
• Use JSDoc comments — prose becomes description; common tags such as @format, @pattern, @minimum, @maximum, @minLength, @maxLength, @default, @example, @deprecated, @nullable, and @asType become JSON Schema keywords.

Limits and edge cases

This is a focused converter, not a full TypeScript compiler. It deliberately rejects constructs that need real type checking or cross-file resolution: generics, utility/mapped types such as Partial or Pick, keyof, typeof, indexed access, conditional types, imports, exports from other files, functions, methods, classes, namespaces, and decorators. Unsupported input returns a line-numbered error naming the construct instead of guessing.

References between declarations in the same paste are supported and emitted as $ref plus reachable $defs/definitions. Recursive local references are allowed. any and unknown become open schemas, never becomes an impossible schema, Date becomes a string with format: date-time, and bigint becomes integer.

FAQ