--- title: Capacitor Node.js Plugin for Android & iOS description: Run a full Node.js runtime in your Capacitor app on Android and iOS. Use npm packages and exchange messages with the Node.js engine. tags: - Android - iOS search: boost: 2 faq: true status: new github_repo: capawesome-team/capacitor-plugins npm_package: "@capawesome/capacitor-nodejs" --- # Capacitor Node.js Plugin Capacitor plugin for running [Node.js](https://nodejs.org/) in mobile apps.[^1][^2]
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## Features The Capacitor Node.js plugin is one of the most complete solutions for running Node.js in Capacitor apps. Here are some of the key features: - ๐Ÿ–ฅ๏ธ **Cross-platform**: Supports Android and iOS. - ๐Ÿš€ **Node.js runtime**: Embeds a complete Node.js runtime based on [Node.js for Mobile Apps](https://github.com/nodejs-mobile/nodejs-mobile). - ๐Ÿงต **Background thread**: Runs the Node.js engine on a dedicated background thread to avoid blocking the UI. - ๐Ÿ” **Bidirectional communication**: Event-based message passing between the Capacitor app and the Node.js runtime. - ๐Ÿ“ฆ **npm ecosystem**: Use npm packages that are not browser-compatible and rely on Node.js core modules. - ๐Ÿ› ๏ธ **Configurable**: Start the Node.js runtime automatically or manually with custom arguments, environment variables and script. - ๐Ÿค **Compatibility**: Works alongside the [Background Task](https://capawesome.io/docs/sdks/capacitor/background-task/), [SQLite](https://capawesome.io/docs/sdks/capacitor/sqlite/) and [Zip](https://capawesome.io/docs/sdks/capacitor/zip/) plugins. - ๐Ÿ” **Up-to-date**: Always supports the latest Capacitor version. Missing a feature? Just [open an issue](https://github.com/capawesome-team/capacitor-plugins/issues) and we'll take a look! ## Use Cases The Node.js plugin is typically used whenever an app needs functionality that only the Node.js ecosystem provides, for example: - **Node.js-only libraries**: Use npm packages that are not browser-compatible because they rely on Node.js core modules. - **Code reuse**: Reuse existing Node.js code in your mobile app instead of rewriting it for the browser. - **Background processing**: Offload heavy work to the Node.js engine, which runs on a dedicated background thread and does not block the UI. - **Local data processing**: Process and persist data on the device using the writable directory provided by the Node.js runtime. ## Compatibility | Plugin Version | Capacitor Version | Status | | -------------- | ----------------- | -------------- | | 0.0.x | >=8.x.x | Active support | ## Installation You can use our **AI-Assisted Setup** to install the plugin. Add the [Capawesome Skills](https://github.com/capawesome-team/skills) to your AI tool using the following command: ```bash npx skills add capawesome-team/skills --skill capacitor-plugins ``` Then use the following prompt: ``` Use the `capacitor-plugins` skill from `capawesome-team/skills` to install the `@capawesome/capacitor-nodejs` plugin in my project. ``` If you prefer **Manual Setup**, install the plugin by running the following commands and follow the platform-specific instructions below: ```bash npm install @capawesome/capacitor-nodejs npx cap sync ``` **Attention**: This plugin embeds the [Node.js for Mobile Apps](https://github.com/nodejs-mobile/nodejs-mobile) runtime binaries. The binaries are not included in the npm package but downloaded on demand: the Android binaries are downloaded by the Gradle build and the iOS binaries are downloaded during `npm install` (only on macOS). Set the `CAPACITOR_NODEJS_SKIP_DOWNLOAD` environment variable to `1` to skip the iOS download. ### Android #### Variables If needed, you can define the following project variables in your app's `variables.gradle` file to change the default version of the runtime: - `$nodejsMobileVersion` version of the Node.js for Mobile Apps runtime (default: `18.20.4-capawesome.1`, a [16 KB page size compatible build](https://github.com/capawesome-team/nodejs-mobile/releases)) - `$nodejsMobileAndroidUrl` download URL of the Android runtime binaries (default: GitHub release of `$nodejsMobileVersion`) - `$nodejsMobileAndroidSha256` SHA-256 checksum of the Android runtime binaries download (default: checksum of `$nodejsMobileVersion`) ### iOS This plugin currently only supports **Swift Package Manager**. CocoaPods is not supported. If you install dependencies with disabled lifecycle scripts (e.g. `npm install --ignore-scripts`), the iOS runtime binaries are not downloaded automatically. In this case, run the download script manually before building your app: ```bash node node_modules/@capawesome/capacitor-nodejs/scripts/postinstall.js ``` ## Configuration | Prop | Type | Description | Default | Since | | --------------- | ------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------- | ----- | | **`nodeDir`** | string | The directory of the Node.js project, relative to the Capacitor `webDir`. Only available on Android and iOS. | 'nodejs' | 0.0.1 | | **`startMode`** | 'manual' \| 'auto' | The start mode of the Node.js runtime. If set to `auto`, the Node.js runtime starts automatically when the app is launched. If set to `manual`, the Node.js runtime must be started manually using the `start(...)` method. Only available on Android and iOS. | 'auto' | 0.0.1 | ### Examples In `capacitor.config.json`: ```json { "plugins": { "Nodejs": { "nodeDir": 'custom-nodejs', "startMode": 'manual' } } } ``` In `capacitor.config.ts`: ```ts /// import { CapacitorConfig } from '@capacitor/cli'; const config: CapacitorConfig = { plugins: { Nodejs: { nodeDir: 'custom-nodejs', startMode: 'manual', }, }, }; export default config; ``` ## Demo A working example can be found [here](https://github.com/capawesome-team/capacitor-plugins/tree/main/packages/nodejs/example). ## Usage The following examples show how to set up the Node.js project, communicate between Node.js and the Capacitor app, start the runtime manually, wait for it to be ready, and exchange messages with it. ### Set up the Node.js project The plugin runs the Node.js project located in the `nodejs` directory (see the `nodeDir` configuration option) inside your Capacitor `webDir`. Make sure your web build outputs the Node.js project to this directory, for example by placing it in the `public` directory of your web project: ``` my-app โ”œโ”€โ”€ capacitor.config.json // webDir: 'dist' โ””โ”€โ”€ src โ””โ”€โ”€ public โ””โ”€โ”€ nodejs โ”œโ”€โ”€ package.json โ””โ”€โ”€ index.js ``` The `package.json` file of the Node.js project defines the script file to run in the `main` field: ```json { "name": "nodejs-project", "version": "1.0.0", "main": "index.js" } ``` ### Communicate with the Capacitor app from Node.js Inside the script file (`index.js` in this example), the built-in `bridge` module provides the communication channel to the Capacitor app: ```js const { app, channel } = require('bridge'); // Receive messages from the Capacitor app. channel.on('my-event', (...args) => { // Send messages to the Capacitor app. channel.post('my-response', 'Hello from Node.js!'); }); // Get a writable directory for persistent file storage. const dataDir = app.datadir(); // Listen for app lifecycle events. app.on('pause', pauseLock => { pauseLock.release(); }); app.on('resume', () => {}); ``` **Attention**: The Node.js project directory may be overwritten during app updates. Store persistent data in the directory returned by `app.datadir()`. ### Start the Node.js runtime manually By default, the Node.js runtime starts automatically when the app is launched. If the `startMode` configuration option is set to `manual`, start it yourself with custom arguments, environment variables and script: ```typescript import { Nodejs } from '@capawesome/capacitor-nodejs'; const start = async () => { // Only available if the `startMode` configuration option is set to `manual`. await Nodejs.start({ args: ['--option', 'value'], env: { MY_ENV_VAR: 'value' }, script: 'custom-main.js', }); }; ``` ### Wait for the Node.js runtime to be ready The Node.js runtime is considered ready as soon as the Node.js project has required the `bridge` module. Check the current state with `isReady()` or listen for the `ready` event: ```typescript import { Nodejs } from '@capawesome/capacitor-nodejs'; const isReady = async () => { const { ready } = await Nodejs.isReady(); return ready; }; const addReadyListener = async () => { await Nodejs.addListener('ready', () => { console.log('The Node.js runtime is ready.'); }); }; ``` ### Exchange messages with the Node.js runtime Once the Node.js runtime is ready, send messages to it and listen for messages received from it: ```typescript import { Nodejs } from '@capawesome/capacitor-nodejs'; const send = async () => { await Nodejs.send({ eventName: 'my-event', args: ['Hello from Capacitor!'], }); }; const addMessageListener = async () => { await Nodejs.addListener('message', event => { console.log('Received message:', event.eventName, event.args); }); }; ``` ### Use npm packages To use npm packages, run `npm install --omit=dev` inside the Node.js project directory before building your web project. It's recommended to bundle the Node.js project into a single file (e.g. with [esbuild](https://esbuild.github.io/)) to improve the startup time. ## API * [`isReady()`](#isready) * [`send(...)`](#send) * [`start(...)`](#start) * [`addListener('message', ...)`](#addlistenermessage-) * [`addListener('ready', ...)`](#addlistenerready-) * [`removeAllListeners()`](#removealllisteners) * [Interfaces](#interfaces) * [Type Aliases](#type-aliases) ### isReady() ```typescript isReady() => Promise ``` Check if the Node.js runtime is ready to receive messages. The Node.js runtime is considered ready as soon as the Node.js project has required the `bridge` module. Only available on Android and iOS. **Returns:** Promise<IsReadyResult> **Since:** 0.0.1 -------------------- ### send(...) ```typescript send(options: SendOptions) => Promise ``` Send a message to the Node.js runtime. This method is only available when the Node.js runtime is ready. Use the `isReady()` method or the `ready` event to check if the Node.js runtime is ready. Only available on Android and iOS. | Param | Type | | ------------- | --------------------------------------------------- | | **`options`** | SendOptions | **Since:** 0.0.1 -------------------- ### start(...) ```typescript start(options?: StartOptions | undefined) => Promise ``` Start the Node.js runtime manually. This method is only available if the `startMode` configuration option is set to `manual`. **Attention**: The Node.js runtime can only be started once per app launch. Stopping and restarting the Node.js runtime is not supported. Only available on Android and iOS. | Param | Type | | ------------- | ----------------------------------------------------- | | **`options`** | StartOptions | **Since:** 0.0.1 -------------------- ### addListener('message', ...) ```typescript addListener(eventName: 'message', listenerFunc: (event: MessageEvent) => void) => Promise ``` Called when a message is received from the Node.js runtime. Only available on Android and iOS. | Param | Type | | ------------------ | ------------------------------------------------------------------------- | | **`eventName`** | 'message' | | **`listenerFunc`** | (event: MessageEvent) => void | **Returns:** Promise<PluginListenerHandle> **Since:** 0.0.1 -------------------- ### addListener('ready', ...) ```typescript addListener(eventName: 'ready', listenerFunc: () => void) => Promise ``` Called when the Node.js runtime is ready to receive messages. Only available on Android and iOS. | Param | Type | | ------------------ | -------------------------- | | **`eventName`** | 'ready' | | **`listenerFunc`** | () => void | **Returns:** Promise<PluginListenerHandle> **Since:** 0.0.1 -------------------- ### removeAllListeners() ```typescript removeAllListeners() => Promise ``` Remove all listeners for this plugin. **Since:** 0.0.1 -------------------- ### Interfaces #### IsReadyResult | Prop | Type | Description | Since | | ----------- | -------------------- | ---------------------------------------------------------------- | ----- | | **`ready`** | boolean | Whether or not the Node.js runtime is ready to receive messages. | 0.0.1 | #### SendOptions | Prop | Type | Description | Since | | --------------- | ------------------------- | ----------------------------------------------------- | ----- | | **`args`** | MessageArg[] | The arguments to send to the Node.js runtime. | 0.0.1 | | **`eventName`** | string | The name of the event to send to the Node.js runtime. | 0.0.1 | #### StartOptions | Prop | Type | Description | Default | Since | | ------------ | --------------------------------------- | ------------------------------------------------------------------------------ | -------------------------------------------------------------------------------- | ----- | | **`args`** | string[] | The arguments to pass to the Node.js process. | | 0.0.1 | | **`env`** | { [key: string]: string; } | The environment variables to set for the Node.js process. | | 0.0.1 | | **`script`** | string | The path of the script file to run, relative to the Node.js project directory. | The `main` field of the `package.json` file of the Node.js project. | 0.0.1 | #### PluginListenerHandle | Prop | Type | | ------------ | ----------------------------------------- | | **`remove`** | () => Promise<void> | #### MessageEvent | Prop | Type | Description | Since | | --------------- | ------------------------- | -------------------------------------------------------- | ----- | | **`args`** | MessageArg[] | The arguments received from the Node.js runtime. | 0.0.1 | | **`eventName`** | string | The name of the event received from the Node.js runtime. | 0.0.1 | ### Type Aliases #### MessageArg A single argument of a message that is exchanged with the Node.js runtime. The value must be JSON-serializable. string | number | boolean | null | MessageArg[] | { [key: string]: MessageArg } ## Limitations The underlying [Node.js for Mobile Apps](https://github.com/nodejs-mobile/nodejs-mobile) runtime has some limitations that you should be aware of: - **Single instance**: The Node.js runtime can only be started once per app launch. Stopping and restarting the runtime is not supported. - **No child processes**: The `child_process` module is not supported on mobile platforms. - **No JIT on iOS**: On iOS, the JavaScript engine runs in interpreter-only mode (no JIT compilation), which results in slower JavaScript execution compared to Android. - **App size**: Embedding the Node.js runtime increases the app size by several tens of megabytes per CPU architecture. - **Native addons**: Node.js native addons are only supported on Android if they are provided as prebuilds (see [`node-gyp-build`](https://github.com/prebuild/node-gyp-build)) for the target architectures. - **`process.exit()`**: Calling `process.exit()` is not allowed by the Apple App Store guidelines. ## FAQ ### Which Node.js version is supported? The plugin currently runs Node.js `18.20.4`, the latest version available from [Node.js for Mobile Apps](https://github.com/nodejs-mobile/nodejs-mobile). Support for newer Node.js versions requires self-built runtime binaries for mobile platforms, which we are evaluating. ### Why is there no `stop()` method? The underlying runtime only supports a single Node.js instance per app launch and provides no API to stop or restart it. A `stop()` method would therefore leave the app in a state where Node.js could never be started again until the app is restarted. If you need to stop work in the Node.js runtime, send a message (e.g. a `shutdown` event) and let your Node.js code stop its servers and timers. The idle runtime consumes negligible resources. ### Where should I store persistent data in the Node.js project? Store persistent data in the directory returned by `app.datadir()` of the built-in `bridge` module. The Node.js project directory itself may be overwritten during app updates, so any files written there can be lost. ### Why is JavaScript execution slower on iOS than on Android? On iOS, the JavaScript engine runs in interpreter-only mode without JIT compilation, which results in slower JavaScript execution compared to Android. This is a limitation of the underlying Node.js for Mobile Apps runtime. See the [Limitations](#limitations) section for more details. ### Can I use this plugin with Ionic, React, Vue or Angular? Yes, the plugin is framework-agnostic. It works in any Capacitor app regardless of the web framework, including Ionic with Angular, React, or Vue, as well as plain JavaScript projects. ## Related Plugins - [Background Task](https://capawesome.io/docs/sdks/capacitor/background-task/): Run background tasks in your Capacitor app. - [SQLite](https://capawesome.io/docs/sdks/capacitor/sqlite/): Access SQLite databases with support for encryption, transactions, and schema migrations. - [Zip](https://capawesome.io/docs/sdks/capacitor/zip/): Zip and unzip files and directories. ## Newsletter Stay up to date with the latest news and updates about the Capawesome, Capacitor, and Ionic ecosystem by subscribing to our [Capawesome Newsletter](https://cloud.capawesome.io/newsletter/). ## Changelog See [CHANGELOG.md](https://github.com/capawesome-team/capacitor-plugins/blob/main/packages/nodejs/CHANGELOG.md). ## License See [LICENSE](https://github.com/capawesome-team/capacitor-plugins/blob/main/packages/nodejs/LICENSE). [^1]: This project is not affiliated with, endorsed by, sponsored by, or approved by the OpenJS Foundation or any of their affiliates or subsidiaries. [^2]: `Node.js` is a registered trademark of the OpenJS Foundation.