electron/docs/api/app.md

app

Control your application's event lifecycle.

The following example shows how to quit the application when the last window is closed:

const {app} = require('electron');
app.on('window-all-closed', () => {
  app.quit();
});

Events

The app object emits the following events:

Event: 'will-finish-launching'

Emitted when the application has finished basic startup. On Windows and Linux, the will-finish-launching event is the same as the ready event; on macOS, this event represents the applicationWillFinishLaunching notification of NSApplication. You would usually set up listeners for the open-file and open-url events here, and start the crash reporter and auto updater.

In most cases, you should just do everything in the ready event handler.

Event: 'ready'

Emitted when Electron has finished initialization.

Event: 'window-all-closed'

Emitted when all windows have been closed.

If you do not subscribe to this event and all windows are closed, the default behavior is to quit the app; however, if you subscribe, you control whether the app quits or not. If the user pressed Cmd + Q, or the developer called app.quit(), Electron will first try to close all the windows and then emit the will-quit event, and in this case the window-all-closed event would not be emitted.

Event: 'before-quit'

Returns:

• event Event

Emitted before the application starts closing its windows. Calling event.preventDefault() will prevent the default behaviour, which is terminating the application.

Event: 'will-quit'

Returns:

• event Event

Emitted when all windows have been closed and the application will quit. Calling event.preventDefault() will prevent the default behaviour, which is terminating the application.

See the description of the window-all-closed event for the differences between the will-quit and window-all-closed events.

Event: 'quit'

Returns:

• event Event
• exitCode Integer

Emitted when the application is quitting.

Event: 'open-file' macOS

Returns:

• event Event
• path String

Emitted when the user wants to open a file with the application. The open-file event is usually emitted when the application is already open and the OS wants to reuse the application to open the file. open-file is also emitted when a file is dropped onto the dock and the application is not yet running. Make sure to listen for the open-file event very early in your application startup to handle this case (even before the ready event is emitted).

You should call event.preventDefault() if you want to handle this event.

On Windows, you have to parse process.argv (in the main process) to get the filepath.

Event: 'open-url' macOS

Returns:

• event Event
• url String

Emitted when the user wants to open a URL with the application. The URL scheme must be registered to be opened by your application.

You should call event.preventDefault() if you want to handle this event.

Event: 'activate' macOS

Returns:

• event Event
• hasVisibleWindows Boolean

Emitted when the application is activated, which usually happens when the user clicks on the application's dock icon.

Event: 'continue-activity' macOS

Returns:

• event Event
• type String - A string identifying the activity. Maps to NSUserActivity.activityType.
• userInfo Object - Contains app-specific state stored by the activity on another device.

Emitted during Handoff when an activity from a different device wants to be resumed. You should call event.preventDefault() if you want to handle this event.

A user activity can be continued only in an app that has the same developer Team ID as the activity's source app and that supports the activity's type. Supported activity types are specified in the app's Info.plist under the NSUserActivityTypes key.

Event: 'browser-window-blur'

Returns:

• event Event
• window BrowserWindow

Emitted when a browserWindow gets blurred.

Event: 'browser-window-focus'

Returns:

• event Event
• window BrowserWindow

Emitted when a browserWindow gets focused.

Event: 'browser-window-created'

Returns:

• event Event
• window BrowserWindow

Emitted when a new browserWindow is created.

Event: 'web-contents-created'

Returns:

• event Event
• webContents WebContents

Emitted when a new webContents is created.

Event: 'certificate-error'

Returns:

• event Event
• webContents WebContents
• url URL
• error String - The error code
• certificate Object
  • data Buffer - PEM encoded data
  • issuerName String
• callback Function

Emitted when failed to verify the certificate for url, to trust the certificate you should prevent the default behavior with event.preventDefault() and call callback(true).

app.on('certificate-error', (event, webContents, url, error, certificate, callback) => {
  if (url === 'https://github.com') {
    // Verification logic.
    event.preventDefault();
    callback(true);
  } else {
    callback(false);
  }
});

Event: 'select-client-certificate'

Returns:

• event Event
• webContents WebContents
• url URL
• certificateList [Objects]
  • data Buffer - PEM encoded data
  • issuerName String - Issuer's Common Name
• callback Function

Emitted when a client certificate is requested.

The url corresponds to the navigation entry requesting the client certificate and callback needs to be called with an entry filtered from the list. Using event.preventDefault() prevents the application from using the first certificate from the store.

app.on('select-client-certificate', (event, webContents, url, list, callback) => {
  event.preventDefault();
  callback(list[0]);
});

Event: 'login'

Returns:

• event Event
• webContents WebContents
• request Object
  • method String
  • url URL
  • referrer URL
• authInfo Object
  • isProxy Boolean
  • scheme String
  • host String
  • port Integer
  • realm String
• callback Function

Emitted when webContents wants to do basic auth.

The default behavior is to cancel all authentications, to override this you should prevent the default behavior with event.preventDefault() and call callback(username, password) with the credentials.

app.on('login', (event, webContents, request, authInfo, callback) => {
  event.preventDefault();
  callback('username', 'secret');
});

Event: 'gpu-process-crashed'

Emitted when the gpu process crashes.

Methods

The app object has the following methods:

Note: Some methods are only available on specific operating systems and are labeled as such.

app.quit()

Try to close all windows. The before-quit event will be emitted first. If all windows are successfully closed, the will-quit event will be emitted and by default the application will terminate.

This method guarantees that all beforeunload and unload event handlers are correctly executed. It is possible that a window cancels the quitting by returning false in the beforeunload event handler.

app.exit(exitCode)

• exitCode Integer

Exits immediately with exitCode.

All windows will be closed immediately without asking user and the before-quit and will-quit events will not be emitted.

app.relaunch([options])

• options Object (optional)
  • args Array (optional)
  • execPath String (optional)

Relaunches the app when current instance exits.

By default the new instance will use the same working directory and command line arguments with current instance. When args is specified, the args will be passed as command line arguments instead. When execPath is specified, the execPath will be executed for relaunch instead of current app.

Note that this method does not quit the app when executed, you have to call app.quit or app.exit after calling app.relaunch to make the app restart.

When app.relaunch is called for multiple times, multiple instances will be started after current instance exited.

An example of restarting current instance immediately and adding a new command line argument to the new instance:

app.relaunch({args: process.argv.slice(1) + ['--relaunch']})
app.exit(0)

app.focus()

On Linux, focuses on the first visible window. On macOS, makes the application the active app. On Windows, focuses on the application's first window.

app.hide() macOS

Hides all application windows without minimizing them.

app.show() macOS

Shows application windows after they were hidden. Does not automatically focus them.

app.getAppPath()

Returns the current application directory.

app.getPath(name)

• name String

Retrieves a path to a special directory or file associated with name. On failure an Error is thrown.

You can request the following paths by the name:

• home User's home directory.
• appData Per-user application data directory, which by default points to:
  • %APPDATA% on Windows
  • $XDG_CONFIG_HOME or ~/.config on Linux
  • ~/Library/Application Support on macOS
• userData The directory for storing your app's configuration files, which by default it is the appData directory appended with your app's name.
• temp Temporary directory.
• exe The current executable file.
• module The libchromiumcontent library.
• desktop The current user's Desktop directory.
• documents Directory for a user's "My Documents".
• downloads Directory for a user's downloads.
• music Directory for a user's music.
• pictures Directory for a user's pictures.
• videos Directory for a user's videos.
• pepperFlashSystemPlugin Full path to the system version of the Pepper Flash plugin.

app.setPath(name, path)

• name String
• path String

Overrides the path to a special directory or file associated with name. If the path specifies a directory that does not exist, the directory will be created by this method. On failure an Error is thrown.

You can only override paths of a name defined in app.getPath.

By default, web pages' cookies and caches will be stored under the userData directory. If you want to change this location, you have to override the userData path before the ready event of the app module is emitted.

app.getVersion()

Returns the version of the loaded application. If no version is found in the application's package.json file, the version of the current bundle or executable is returned.

app.getName()

Returns the current application's name, which is the name in the application's package.json file.

Usually the name field of package.json is a short lowercased name, according to the npm modules spec. You should usually also specify a productName field, which is your application's full capitalized name, and which will be preferred over name by Electron.

app.setName(name)

• name String

Overrides the current application's name.

app.getLocale()

Returns the current application locale. Possible return values are documented here

Note: When distributing your packaged app, you have to also ship the locales folder.

Note: On Windows you have to call it after the ready events gets emitted.

app.addRecentDocument(path) macOS Windows

• path String

Adds path to the recent documents list.

This list is managed by the OS. On Windows you can visit the list from the task bar, and on macOS you can visit it from dock menu.

app.clearRecentDocuments() macOS Windows

Clears the recent documents list.

app.setAsDefaultProtocolClient(protocol) macOS Windows

• protocol String - The name of your protocol, without ://. If you want your app to handle electron:// links, call this method with electron as the parameter.

This method sets the current executable as the default handler for a protocol (aka URI scheme). It allows you to integrate your app deeper into the operating system. Once registered, all links with your-protocol:// will be opened with the current executable. The whole link, including protocol, will be passed to your application as a parameter.

Note: On macOS, you can only register protocols that have been added to your app's info.plist, which can not be modified at runtime. You can however change the file with a simple text editor or script during build time. Please refer to Apple's documentation for details.

The API uses the Windows Registry and LSSetDefaultHandlerForURLScheme internally.

app.removeAsDefaultProtocolClient(protocol) macOS Windows

• protocol String - The name of your protocol, without ://.

This method checks if the current executable as the default handler for a protocol (aka URI scheme). If so, it will remove the app as the default handler.

app.isDefaultProtocolClient(protocol) macOS Windows

• protocol String - The name of your protocol, without ://.

This method checks if the current executable is the default handler for a protocol (aka URI scheme). If so, it will return true. Otherwise, it will return false.

Note: On macOS, you can use this method to check if the app has been registered as the default protocol handler for a protocol. You can also verify this by checking ~/Library/Preferences/com.apple.LaunchServices.plist on the macOS machine. Please refer to Apple's documentation for details.

The API uses the Windows Registry and LSCopyDefaultHandlerForURLScheme internally.

app.setUserTasks(tasks) Windows

• tasks Array - Array of Task objects

Adds tasks to the Tasks category of the JumpList on Windows.

tasks is an array of Task objects in the following format:

Task Object:

• program String - Path of the program to execute, usually you should specify process.execPath which opens the current program.
• arguments String - The command line arguments when program is executed.
• title String - The string to be displayed in a JumpList.
• description String - Description of this task.
• iconPath String - The absolute path to an icon to be displayed in a JumpList, which can be an arbitrary resource file that contains an icon. You can usually specify process.execPath to show the icon of the program.
• iconIndex Integer - The icon index in the icon file. If an icon file consists of two or more icons, set this value to identify the icon. If an icon file consists of one icon, this value is 0.

app.makeSingleInstance(callback)

• callback Function

This method makes your application a Single Instance Application - instead of allowing multiple instances of your app to run, this will ensure that only a single instance of your app is running, and other instances signal this instance and exit.

callback will be called with callback(argv, workingDirectory) when a second instance has been executed. argv is an Array of the second instance's command line arguments, and workingDirectory is its current working directory. Usually applications respond to this by making their primary window focused and non-minimized.

The callback is guaranteed to be executed after the ready event of app gets emitted.

This method returns false if your process is the primary instance of the application and your app should continue loading. And returns true if your process has sent its parameters to another instance, and you should immediately quit.

On macOS the system enforces single instance automatically when users try to open a second instance of your app in Finder, and the open-file and open-url events will be emitted for that. However when users start your app in command line the system's single instance mechanism will be bypassed and you have to use this method to ensure single instance.

An example of activating the window of primary instance when a second instance starts:

let myWindow = null;

const shouldQuit = app.makeSingleInstance((commandLine, workingDirectory) => {
  // Someone tried to run a second instance, we should focus our window.
  if (myWindow) {
    if (myWindow.isMinimized()) myWindow.restore();
    myWindow.focus();
  }
});

if (shouldQuit) {
  app.quit();
  return;
}

// Create myWindow, load the rest of the app, etc...
app.on('ready', () => {
});

app.releaseSingleInstance()

Releases all locks that were created by makeSingleInstance. This will allow multiple instances of the application to once again run side by side.

app.setUserActivity(type, userInfo[, webpageURL]) macOS

• type String - Uniquely identifies the activity. Maps to NSUserActivity.activityType.
• userInfo Object - App-specific state to store for use by another device.
• webpageURL String - The webpage to load in a browser if no suitable app is installed on the resuming device. The scheme must be http or https.

Creates an NSUserActivity and sets it as the current activity. The activity is eligible for Handoff to another device afterward.

app.getCurrentActivityType() macOS

Returns the type of the currently running activity.

app.setAppUserModelId(id) Windows

• id String

Changes the Application User Model ID to id.

app.importCertificate(options, callback) LINUX

• options Object
  • certificate String - Path for the pkcs12 file.
  • password String - Passphrase for the certificate.
• callback Function
  • result Integer - Result of import.

Imports the certificate in pkcs12 format into the platform certificate store. callback is called with the result of import operation, a value of 0 indicates success while any other value indicates failure according to chromium net_error_list.

app.disableHardwareAcceleration()

Disables hardware acceleration for current app.

This method can only be called before app is ready.

app.setBadgeCount(count) Linux macOS

• count Integer

Sets the counter badge for current app. Setting the count to 0 will hide the badge. Returns true when the call succeeded, otherwise returns false.

On macOS it shows on the dock icon. On Linux it only works for Unity launcher,

Note: Unity launcher requires the exsistence of a .desktop file to work, for more information please read Desktop Environment Integration.

app.getBadgeCount() Linux macOS

Returns the current value displayed in the counter badge.

app.isUnityRunning() Linux

Returns whether current desktop environment is Unity launcher.

app.commandLine.appendSwitch(switch[, value])

Append a switch (with optional value) to Chromium's command line.

Note: This will not affect process.argv, and is mainly used by developers to control some low-level Chromium behaviors.

app.commandLine.appendArgument(value)

Append an argument to Chromium's command line. The argument will be quoted correctly.

Note: This will not affect process.argv.

app.dock.bounce([type]) macOS

• type String (optional) - Can be critical or informational. The default is informational

When critical is passed, the dock icon will bounce until either the application becomes active or the request is canceled.

When informational is passed, the dock icon will bounce for one second. However, the request remains active until either the application becomes active or the request is canceled.

Returns an ID representing the request.

app.dock.cancelBounce(id) macOS

• id Integer

Cancel the bounce of id.

app.dock.downloadFinished(filePath) macOS

• filePath String

Bounces the Downloads stack if the filePath is inside the Downloads folder.

app.dock.setBadge(text) macOS

• text String

Sets the string to be displayed in the dock’s badging area.

app.dock.getBadge() macOS

Returns the badge string of the dock.

app.dock.hide() macOS

Hides the dock icon.

app.dock.show() macOS

Shows the dock icon.

app.dock.setMenu(menu) macOS

• menu Menu

Sets the application's dock menu.

app.dock.setIcon(image) macOS

• image NativeImage

Sets the image associated with this dock icon.