expo-module

Run npx create-expo-module with an explicit slug, choosing --local for app-specific modules or a standalone package for reuse. Pass --platform apple android and --features like Function or AsyncFunction to generate starter code, then replace the examples with your real implementation.

Use npx create-expo-module add-platform-support with --platform android, apple, or web from the module root. It only adds platforms missing from expo-module.config.json, refuses to overwrite existing native directories, and works only with modules using the Expo Modules API DSL.

Local modules live inside one app, use the app's tooling, and skip dependency installation and example apps. Standalone modules have their own package.json, install dependencies, build TypeScript, and usually include an example app for testing and publishing to npm.

Declare events with Events("onChange") in the module definition, then call sendEvent from Swift or Kotlin with a payload dictionary. In JavaScript, subscribe with the useEvent hook or addListener, and use OnStartObserving and OnStopObserving to control event production.

Do not use it to migrate an existing Swift module from the definition DSL to the Expo Modules API 2.0 macros like @ExpoModule and @JS. For that migration, use the expo-migrate-module skill from the expo-experiments plugin instead.