Writing Expo Modules

Complete reference for building native modules and views using the Expo Modules API. Covers Swift (iOS), Kotlin (Android), and TypeScript.

When to Use

• Creating a new Expo native module or native view
• Adding native functionality (camera, sensors, system APIs) to an Expo app
• Wrapping platform SDKs for React Native consumption
• Building config plugins that modify native project files
• Adding Android, Apple, or web support to an existing Expo module
• Editing expo-module.config.json, config plugins, or lifecycle hooks

To migrate an existing Swift module from the definition DSL to the Expo Modules API 2.0 macros (@ExpoModule, @JS, @Event), use the expo-migrate-module skill (from the expo-experiments plugin) instead.

References

Consult these resources as needed:

references/
  create-expo-module.md      Scaffolding and add-platform-support workflow, defaults, and quirks
  native-module.md           Module definition DSL: Name, Function, AsyncFunction, Property, Constant, Events, type system, shared objects
  native-view.md             Native view components: View, Prop, EventDispatcher, view lifecycle, ref-based functions
  lifecycle.md               Lifecycle hooks: module, iOS app/AppDelegate, Android activity/application listeners
  config-plugin.md           Config plugins: modifying Info.plist, AndroidManifest.xml, reading values in native code
  module-config.md           expo-module.config.json fields, file placement, and autolinking behavior

Quick Start

Prefer create-expo-module over manually creating native module files and directories. In practice, the best path is usually to create the scaffold first and then build on top of it. The scaffold sets up the expected layout, expo-module.config.json, podspec or Gradle files, TypeScript bindings, and the standalone example app flow.