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Ready to ship.

The narrowest declarations, with your default values in every tooltip. Generate .d.ts files with Bun, from your first export to your next release.

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src/index.ts.ts

dist/index.d.tsDECLARATION

d.ts

export declare
function greet(options: Options): string;

Public API, preserved.

Built for BunCLI + TypeScript APIMIT licensedOpen source, all the way down

A small step in your build.
A proper home for your types.

Keep writing your library. Let dtsx handle the declarations.

Your code stays yours.

Emit declarations from TypeScript, TSX, Vue, and STX. Keep the comments that make your public API useful.

Choose your shape.

Mirror your source files or bundle declarations into one public entry.

Stay in the loop.

Watch mode and incremental generation keep declaration work in your development flow.

Explore configuration

Narrow types.
Defaults included.

dtsx infers the narrowest sound type from each value, with no compiler and no annotations required. Then it keeps the value itself as @defaultValue, so your users see it in every editor tooltip.

Same source for both src/index.ts

export const config = {
  port: 3000,
  host: 'localhost',
  retries: 3,
}

export const LOG_LEVELS = ['debug', 'info', 'warn'] as const

export let mode = 'production'

export function connect(host = 'localhost', port = 5432) {
  return { host, port, secure: port === 443 }
}

export class Client {
  timeout = 1000
  static version = '1.0.0'
}

tsc 6.0.3 --declarationTypes only

export declare const config: {
    port: number;
    host: string;
    retries: number;
};
export declare const LOG_LEVELS: readonly ["debug", "info", "warn"];
export declare let mode: string;
export declare function connect(host?: string, port?: number): {
    host: string;
    port: number;
    secure: boolean;
};
export declare class Client {
    timeout: number;
    static version: string;
}

dtsx7 defaults kept

export declare function connect(host?: string, port?: number): {
  host: string;
  port: number;
  secure: boolean
};
/** @defaultValue `{ port: 3000, host: 'localhost', retries: 3 }` */
export declare const config: {
  /** @defaultValue 3000 */
  port: number;
  /** @defaultValue 'localhost' */
  host: string;
  /** @defaultValue 3 */
  retries: number
};
export declare const LOG_LEVELS: readonly ['debug', 'info', 'warn'];
/** @defaultValue 'production' */
export declare let mode: string;
export declare class Client {
  /** @defaultValue 1000 */
  timeout: number;
  /** @defaultValue '1.0.0' */
  static version: string;
}

Literal where it can be.Constants and as const values keep their literal types, like readonly ['debug', 'info', 'warn'].
Wide where it must be.Mutable values widen exactly as TypeScript would, so the types stay sound.
The value, not a guess.Defaults are copied from your source, so tooltips show 3000, not just number.

Implementation in.
Public API out.

Readable declarations, generated from real source. This example is emitted by dtsx when the website builds.

Meet the TypeScript API

export interface Options {
  name: string
  retries?: number
}

export function greet(options: Options): string {
  return `Hello, ${options.name}`
}

export declare function greet(options: Options): string;
export declare interface Options {
  name: string
  retries?: number
}

TypeScript → declarationsSame API. Ready for consumers.

Measure the work.
Show the numbers.

Fresh processes. Identical inputs. Declarations checked after every run.

macOS · Explicit annotations

100 modules + one entrypoint

Nine measured samples per tool.
Median wall-clock time, including startup.

Compare platforms and inference

Standalone declaration bundle medians for 100 modules
Tool	Median
dtsx bundle dtsx	147.6 ms
tsdown / Oxc	244.6 ms
tsdown / TypeScript	883.7 ms
tsup	1162.3 ms
tsc + rollup-plugin-dts	1666.7 ms
dts-bundle-generator	2055.4 ms
Vite + unplugin-dts	2361.9 ms
tsc + API Extractor	2600.1 ms

Apple M1 (Virtual) · Bun 1.4.4 · November 8, 2026. This table uses explicitly annotated libraries. The full lab also tests unannotated inference on macOS and Linux. Tools perform different amounts of checking and bundling. For 100 modules, Oxc has the lowest median in the separate per-file emission workload. Read the methodology.

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Your types.Ready to ship.

A small step in your build.A proper home for your types.