구성 플러그인을 npm 패키지로 배포하기

If you use the same config plugin across multiple Expo projects, or want to share it with the React Native community, packaging it as an npm module makes distribution easy. Consumers install it with npm install and reference it by package name in app.json. Expo automatically discovers the app.plugin.js file at the package root without any extra configuration from the consumer.

A config plugin npm package has a minimal structure: a package.json, an app.plugin.js entry point at the package root (this is the file Expo looks for), and optionally a src/ folder for TypeScript source that compiles to the plugin file. The app.plugin.js filename is the Expo convention — do not name it differently or Expo cannot auto-discover it.

The app.plugin.js file must export a single function as its default export using module.exports (CommonJS). This function is the config plugin itself — it takes config and optional options, applies modifications, and returns the modified config. If your package has a TypeScript build step, app.plugin.js simply re-exports from the compiled build/ directory.

The package.json for a config plugin package needs the standard fields plus a few Expo-specific conventions. Set main to your compiled JS entry (not app.plugin.js — that's separate). List @expo/config-plugins in peerDependencies (not regular dependencies) so consumers use their own installed version and avoid duplicate installs. Prefix the package name with expo- or use a scoped name like @yourorg/expo-plugin-name.

@expo/config-plugins exports TypeScript types, making it easy to type your plugin properly. Use the ConfigPlugin generic type with your options interface. TypeScript catches type errors (like passing an invalid manifest key) at compile time rather than at the consumer's prebuild time. Generate declaration files (.d.ts) so consumers get IntelliSense when passing options.

When using TypeScript, your source code is compiled to build/ but Expo looks for app.plugin.js at the root. Create a minimal app.plugin.js that requires the compiled output. This separation keeps TypeScript source clean while providing the correct entry point that Expo's module resolution expects. The file is typically just one or two lines.

Once published to npm, consumers install the package and add it to app.json plugins. Expo resolves the package by name, finds app.plugin.js in the node_modules folder, and runs it during prebuild. The consumer passes options as the second element of the plugin array tuple. This is exactly the same developer experience as Expo's own first-party plugins.

Before publishing to npm, test your plugin locally using npm link or a relative file: path in the test app's package.json. This lets you iterate quickly without publishing. After local testing, use npm pack to create a tarball and inspect its contents to verify the correct files are included. Only publish once you confirm the plugin works end-to-end.

Publish your plugin with npm publish. Make sure the files field in package.json includes app.plugin.js and build/ but excludes src/ (TypeScript source consumers do not need). Use semantic versioning: bump the patch version for bug fixes, minor for new options, and major when you change the config in a breaking way (e.g., rename an option).

A config plugin README should include: the installation command, the exact app.json snippet showing all available options, a table documenting each option with its type, default, and description, and the list of native changes the plugin makes (which permissions it adds, what Info.plist keys it sets). Developers need to understand what the plugin changes before trusting it with their native project.

Config plugin consumers run expo prebuild to apply your plugin — they do not call your code directly at runtime. Breaking changes include: renaming options, removing options, changing the type of an option, or producing different native output that removes a previously added entry. Always document breaking changes in a CHANGELOG.md and increment the major version so consumers can pin to a safe version.

Test your understanding of React Native Mobile Development concepts from this lesson.

In this lesson you learned: how to structure an npm package for a config plugin with app.plugin.js at the root, how to write the plugin in TypeScript and re-export from app.plugin.js, and how to test locally with npm link before publishing. You also saw how to configure package.json with the correct peerDependencies and files fields. Next up we cover the iOS App Store submission process.