electron/docs/api/session.md

session

Manage browser sessions, cookies, cache, proxy settings, etc.

Process: Main

The session module can be used to create new Session objects.

You can also access the session of existing pages by using the session property of WebContents, or from the session module.

const { BrowserWindow } = require('electron')

const win = new BrowserWindow({ width: 800, height: 600 })
win.loadURL('https://github.com')

const ses = win.webContents.session
console.log(ses.getUserAgent())

Methods

The session module has the following methods:

session.fromPartition(partition[, options])

• partition string
• options Object (optional)
  • cache boolean - Whether to enable cache.

Returns Session - A session instance from partition string. When there is an existing Session with the same partition, it will be returned; otherwise a new Session instance will be created with options.

If partition starts with persist:, the page will use a persistent session available to all pages in the app with the same partition. if there is no persist: prefix, the page will use an in-memory session. If the partition is empty then default session of the app will be returned.

To create a Session with options, you have to ensure the Session with the partition has never been used before. There is no way to change the options of an existing Session object.

session.fromPath(path[, options])

• path string
• options Object (optional)
  • cache boolean - Whether to enable cache.

Returns Session - A session instance from the absolute path as specified by the path string. When there is an existing Session with the same absolute path, it will be returned; otherwise a new Session instance will be created with options. The call will throw an error if the path is not an absolute path. Additionally, an error will be thrown if an empty string is provided.

To create a Session with options, you have to ensure the Session with the path has never been used before. There is no way to change the options of an existing Session object.

Properties

The session module has the following properties:

session.defaultSession

A Session object, the default session object of the app.

Class: Session

Get and set properties of a session.

Process: Main
This class is not exported from the 'electron' module. It is only available as a return value of other methods in the Electron API.

You can create a Session object in the session module:

const { session } = require('electron')
const ses = session.fromPartition('persist:name')
console.log(ses.getUserAgent())

Instance Events

The following events are available on instances of Session:

Event: 'will-download'

Returns:

• event Event
• item DownloadItem
• webContents WebContents

Emitted when Electron is about to download item in webContents.

Calling event.preventDefault() will cancel the download and item will not be available from next tick of the process.

const { session } = require('electron')
session.defaultSession.on('will-download', (event, item, webContents) => {
  event.preventDefault()
  require('got')(item.getURL()).then((response) => {
    require('node:fs').writeFileSync('/somewhere', response.body)
  })
})

Event: 'extension-loaded'

Returns:

• event Event
• extension Extension

Emitted after an extension is loaded. This occurs whenever an extension is added to the "enabled" set of extensions. This includes:

• Extensions being loaded from Session.loadExtension.
• Extensions being reloaded:
  • from a crash.
  • if the extension requested it (chrome.runtime.reload()).

Event: 'extension-unloaded'

Returns:

• event Event
• extension Extension

Emitted after an extension is unloaded. This occurs when Session.removeExtension is called.

Event: 'extension-ready'

Returns:

• event Event
• extension Extension

Emitted after an extension is loaded and all necessary browser state is initialized to support the start of the extension's background page.

Event: 'file-system-access-restricted'

Returns:

• event Event
• details Object
  • origin string - The origin that initiated access to the blocked path.
  • isDirectory boolean - Whether or not the path is a directory.
  • path string - The blocked path attempting to be accessed.
• callback Function
  • action string - The action to take as a result of the restricted path access attempt.
    • allow - This will allow path to be accessed despite restricted status.
    • deny - This will block the access request and trigger an AbortError.
    • tryAgain - This will open a new file picker and allow the user to choose another path.

const { app, dialog, BrowserWindow, session } = require('electron')

async function createWindow () {
  const mainWindow = new BrowserWindow()

  await mainWindow.loadURL('https://buzzfeed.com')

  session.defaultSession.on('file-system-access-restricted', async (e, details, callback) => {
    const { origin, path } = details
    const { response } = await dialog.showMessageBox({
      message: `Are you sure you want ${origin} to open restricted path ${path}?`,
      title: 'File System Access Restricted',
      buttons: ['Choose a different folder', 'Allow', 'Cancel'],
      cancelId: 2
    })

    if (response === 0) {
      callback('tryAgain')
    } else if (response === 1) {
      callback('allow')
    } else {
      callback('deny')
    }
  })

  mainWindow.webContents.executeJavaScript(`
    window.showDirectoryPicker({
      id: 'electron-demo',
      mode: 'readwrite',
      startIn: 'downloads',
    }).catch(e => {
      console.log(e)
    })`, true
  )
}

app.whenReady().then(() => {
  createWindow()

  app.on('activate', () => {
    if (BrowserWindow.getAllWindows().length === 0) createWindow()
  })
})

app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

Event: 'preconnect'

Returns:

• event Event
• preconnectUrl string - The URL being requested for preconnection by the renderer.
• allowCredentials boolean - True if the renderer is requesting that the connection include credentials (see the spec for more details.)

Emitted when a render process requests preconnection to a URL, generally due to a resource hint.

Event: 'spellcheck-dictionary-initialized'

Returns:

• event Event
• languageCode string - The language code of the dictionary file

Emitted when a hunspell dictionary file has been successfully initialized. This occurs after the file has been downloaded.

Event: 'spellcheck-dictionary-download-begin'

Returns:

• event Event
• languageCode string - The language code of the dictionary file

Emitted when a hunspell dictionary file starts downloading

Event: 'spellcheck-dictionary-download-success'

Returns:

• event Event
• languageCode string - The language code of the dictionary file

Emitted when a hunspell dictionary file has been successfully downloaded

Event: 'spellcheck-dictionary-download-failure'

Returns:

• event Event
• languageCode string - The language code of the dictionary file

Emitted when a hunspell dictionary file download fails. For details on the failure you should collect a netlog and inspect the download request.

Event: 'select-hid-device'

Returns:

• event Event
• details Object
  • deviceList HIDDevice[]
  • frame WebFrameMain
• callback Function
  • deviceId string | null (optional)

Emitted when a HID device needs to be selected when a call to navigator.hid.requestDevice is made. callback should be called with deviceId to be selected; passing no arguments to callback will cancel the request. Additionally, permissioning on navigator.hid can be further managed by using ses.setPermissionCheckHandler(handler) and ses.setDevicePermissionHandler(handler).

const { app, BrowserWindow } = require('electron')

let win = null

app.whenReady().then(() => {
  win = new BrowserWindow()

  win.webContents.session.setPermissionCheckHandler((webContents, permission, requestingOrigin, details) => {
    if (permission === 'hid') {
      // Add logic here to determine if permission should be given to allow HID selection
      return true
    }
    return false
  })

  // Optionally, retrieve previously persisted devices from a persistent store
  const grantedDevices = fetchGrantedDevices()

  win.webContents.session.setDevicePermissionHandler((details) => {
    if (new URL(details.origin).hostname === 'some-host' && details.deviceType === 'hid') {
      if (details.device.vendorId === 123 && details.device.productId === 345) {
        // Always allow this type of device (this allows skipping the call to `navigator.hid.requestDevice` first)
        return true
      }

      // Search through the list of devices that have previously been granted permission
      return grantedDevices.some((grantedDevice) => {
        return grantedDevice.vendorId === details.device.vendorId &&
              grantedDevice.productId === details.device.productId &&
              grantedDevice.serialNumber && grantedDevice.serialNumber === details.device.serialNumber
      })
    }
    return false
  })

  win.webContents.session.on('select-hid-device', (event, details, callback) => {
    event.preventDefault()
    const selectedDevice = details.deviceList.find((device) => {
      return device.vendorId === 9025 && device.productId === 67
    })
    callback(selectedDevice?.deviceId)
  })
})

Event: 'hid-device-added'

Returns:

• event Event
• details Object
  • device HIDDevice
  • frame WebFrameMain

Emitted after navigator.hid.requestDevice has been called and select-hid-device has fired if a new device becomes available before the callback from select-hid-device is called. This event is intended for use when using a UI to ask users to pick a device so that the UI can be updated with the newly added device.

Event: 'hid-device-removed'

Returns:

• event Event
• details Object
  • device HIDDevice
  • frame WebFrameMain

Emitted after navigator.hid.requestDevice has been called and select-hid-device has fired if a device has been removed before the callback from select-hid-device is called. This event is intended for use when using a UI to ask users to pick a device so that the UI can be updated to remove the specified device.

Event: 'hid-device-revoked'

Returns:

• event Event
• details Object
  • device HIDDevice
  • origin string (optional) - The origin that the device has been revoked from.

Emitted after HIDDevice.forget() has been called. This event can be used to help maintain persistent storage of permissions when setDevicePermissionHandler is used.

Event: 'select-serial-port'

Returns:

• event Event
• portList SerialPort[]
• webContents WebContents
• callback Function
  • portId string

Emitted when a serial port needs to be selected when a call to navigator.serial.requestPort is made. callback should be called with portId to be selected, passing an empty string to callback will cancel the request. Additionally, permissioning on navigator.serial can be managed by using ses.setPermissionCheckHandler(handler) with the serial permission.

const { app, BrowserWindow } = require('electron')

let win = null

app.whenReady().then(() => {
  win = new BrowserWindow({
    width: 800,
    height: 600
  })

  win.webContents.session.setPermissionCheckHandler((webContents, permission, requestingOrigin, details) => {
    if (permission === 'serial') {
      // Add logic here to determine if permission should be given to allow serial selection
      return true
    }
    return false
  })

  // Optionally, retrieve previously persisted devices from a persistent store
  const grantedDevices = fetchGrantedDevices()

  win.webContents.session.setDevicePermissionHandler((details) => {
    if (new URL(details.origin).hostname === 'some-host' && details.deviceType === 'serial') {
      if (details.device.vendorId === 123 && details.device.productId === 345) {
        // Always allow this type of device (this allows skipping the call to `navigator.serial.requestPort` first)
        return true
      }

      // Search through the list of devices that have previously been granted permission
      return grantedDevices.some((grantedDevice) => {
        return grantedDevice.vendorId === details.device.vendorId &&
              grantedDevice.productId === details.device.productId &&
              grantedDevice.serialNumber && grantedDevice.serialNumber === details.device.serialNumber
      })
    }
    return false
  })

  win.webContents.session.on('select-serial-port', (event, portList, webContents, callback) => {
    event.preventDefault()
    const selectedPort = portList.find((device) => {
      return device.vendorId === '9025' && device.productId === '67'
    })
    if (!selectedPort) {
      callback('')
    } else {
      callback(selectedPort.portId)
    }
  })
})

Event: 'serial-port-added'

Returns:

• event Event
• port SerialPort
• webContents WebContents

Emitted after navigator.serial.requestPort has been called and select-serial-port has fired if a new serial port becomes available before the callback from select-serial-port is called. This event is intended for use when using a UI to ask users to pick a port so that the UI can be updated with the newly added port.

Event: 'serial-port-removed'

Returns:

• event Event
• port SerialPort
• webContents WebContents

Emitted after navigator.serial.requestPort has been called and select-serial-port has fired if a serial port has been removed before the callback from select-serial-port is called. This event is intended for use when using a UI to ask users to pick a port so that the UI can be updated to remove the specified port.

Event: 'serial-port-revoked'

Returns:

• event Event
• details Object
  • port SerialPort
  • frame WebFrameMain
  • origin string - The origin that the device has been revoked from.

Emitted after SerialPort.forget() has been called. This event can be used to help maintain persistent storage of permissions when setDevicePermissionHandler is used.

// Browser Process
const { app, BrowserWindow } = require('electron')

app.whenReady().then(() => {
  const win = new BrowserWindow({
    width: 800,
    height: 600
  })

  win.webContents.session.on('serial-port-revoked', (event, details) => {
    console.log(`Access revoked for serial device from origin ${details.origin}`)
  })
})

// Renderer Process

const portConnect = async () => {
  // Request a port.
  const port = await navigator.serial.requestPort()

  // Wait for the serial port to open.
  await port.open({ baudRate: 9600 })

  // ...later, revoke access to the serial port.
  await port.forget()
}

Event: 'select-usb-device'

Returns:

• event Event
• details Object
  • deviceList USBDevice[]
  • frame WebFrameMain
• callback Function
  • deviceId string (optional)

Emitted when a USB device needs to be selected when a call to navigator.usb.requestDevice is made. callback should be called with deviceId to be selected; passing no arguments to callback will cancel the request. Additionally, permissioning on navigator.usb can be further managed by using ses.setPermissionCheckHandler(handler) and ses.setDevicePermissionHandler(handler).

const { app, BrowserWindow } = require('electron')

let win = null

app.whenReady().then(() => {
  win = new BrowserWindow()

  win.webContents.session.setPermissionCheckHandler((webContents, permission, requestingOrigin, details) => {
    if (permission === 'usb') {
      // Add logic here to determine if permission should be given to allow USB selection
      return true
    }
    return false
  })

  // Optionally, retrieve previously persisted devices from a persistent store (fetchGrantedDevices needs to be implemented by developer to fetch persisted permissions)
  const grantedDevices = fetchGrantedDevices()

  win.webContents.session.setDevicePermissionHandler((details) => {
    if (new URL(details.origin).hostname === 'some-host' && details.deviceType === 'usb') {
      if (details.device.vendorId === 123 && details.device.productId === 345) {
        // Always allow this type of device (this allows skipping the call to `navigator.usb.requestDevice` first)
        return true
      }

      // Search through the list of devices that have previously been granted permission
      return grantedDevices.some((grantedDevice) => {
        return grantedDevice.vendorId === details.device.vendorId &&
              grantedDevice.productId === details.device.productId &&
              grantedDevice.serialNumber && grantedDevice.serialNumber === details.device.serialNumber
      })
    }
    return false
  })

  win.webContents.session.on('select-usb-device', (event, details, callback) => {
    event.preventDefault()
    const selectedDevice = details.deviceList.find((device) => {
      return device.vendorId === 9025 && device.productId === 67
    })
    if (selectedDevice) {
      // Optionally, add this to the persisted devices (updateGrantedDevices needs to be implemented by developer to persist permissions)
      grantedDevices.push(selectedDevice)
      updateGrantedDevices(grantedDevices)
    }
    callback(selectedDevice?.deviceId)
  })
})

Event: 'usb-device-added'

Returns:

• event Event
• device USBDevice
• webContents WebContents

Emitted after navigator.usb.requestDevice has been called and select-usb-device has fired if a new device becomes available before the callback from select-usb-device is called. This event is intended for use when using a UI to ask users to pick a device so that the UI can be updated with the newly added device.

Event: 'usb-device-removed'

Returns:

• event Event
• device USBDevice
• webContents WebContents

Emitted after navigator.usb.requestDevice has been called and select-usb-device has fired if a device has been removed before the callback from select-usb-device is called. This event is intended for use when using a UI to ask users to pick a device so that the UI can be updated to remove the specified device.

Event: 'usb-device-revoked'

Returns:

• event Event
• details Object
  • device USBDevice
  • origin string (optional) - The origin that the device has been revoked from.

Emitted after USBDevice.forget() has been called. This event can be used to help maintain persistent storage of permissions when setDevicePermissionHandler is used.

Instance Methods

The following methods are available on instances of Session:

ses.getCacheSize()

Returns Promise<Integer> - the session's current cache size, in bytes.

ses.clearCache()

Returns Promise<void> - resolves when the cache clear operation is complete.

Clears the session’s HTTP cache.

ses.clearStorageData([options])

• options Object (optional)
  • origin string (optional) - Should follow window.location.origin’s representation scheme://host:port.
  • storages string[] (optional) - The types of storages to clear, can be cookies, filesystem, indexdb, localstorage, shadercache, websql, serviceworkers, cachestorage. If not specified, clear all storage types.
  • quotas string[] (optional) - The types of quotas to clear, can be temporary, syncable. If not specified, clear all quotas.

Returns Promise<void> - resolves when the storage data has been cleared.

ses.flushStorageData()

Writes any unwritten DOMStorage data to disk.

ses.setProxy(config)

• config ProxyConfig

Returns Promise<void> - Resolves when the proxy setting process is complete.

Sets the proxy settings.

You may need ses.closeAllConnections to close currently in flight connections to prevent pooled sockets using previous proxy from being reused by future requests.

ses.resolveHost(host, [options])

• host string - Hostname to resolve.
• options Object (optional)
  • queryType string (optional) - Requested DNS query type. If unspecified, resolver will pick A or AAAA (or both) based on IPv4/IPv6 settings:
    • A - Fetch only A records
    • AAAA - Fetch only AAAA records.
  • source string (optional) - The source to use for resolved addresses. Default allows the resolver to pick an appropriate source. Only affects use of big external sources (e.g. calling the system for resolution or using DNS). Even if a source is specified, results can still come from cache, resolving "localhost" or IP literals, etc. One of the following values:
    • any (default) - Resolver will pick an appropriate source. Results could come from DNS, MulticastDNS, HOSTS file, etc
    • system - Results will only be retrieved from the system or OS, e.g. via the getaddrinfo() system call
    • dns - Results will only come from DNS queries
    • mdns - Results will only come from Multicast DNS queries
    • localOnly - No external sources will be used. Results will only come from fast local sources that are available no matter the source setting, e.g. cache, hosts file, IP literal resolution, etc.
  • cacheUsage string (optional) - Indicates what DNS cache entries, if any, can be used to provide a response. One of the following values:
    • allowed (default) - Results may come from the host cache if non-stale
    • staleAllowed - Results may come from the host cache even if stale (by expiration or network changes)
    • disallowed - Results will not come from the host cache.
  • secureDnsPolicy string (optional) - Controls the resolver's Secure DNS behavior for this request. One of the following values:
    • allow (default)
    • disable

Returns Promise<ResolvedHost> - Resolves with the resolved IP addresses for the host.

ses.resolveProxy(url)

• url URL

Returns Promise<string> - Resolves with the proxy information for url.

ses.forceReloadProxyConfig()

Returns Promise<void> - Resolves when the all internal states of proxy service is reset and the latest proxy configuration is reapplied if it's already available. The pac script will be fetched from pacScript again if the proxy mode is pac_script.

ses.setDownloadPath(path)

• path string - The download location.

Sets download saving directory. By default, the download directory will be the Downloads under the respective app folder.

ses.enableNetworkEmulation(options)

• options Object
  • offline boolean (optional) - Whether to emulate network outage. Defaults to false.
  • latency Double (optional) - RTT in ms. Defaults to 0 which will disable latency throttling.
  • downloadThroughput Double (optional) - Download rate in Bps. Defaults to 0 which will disable download throttling.
  • uploadThroughput Double (optional) - Upload rate in Bps. Defaults to 0 which will disable upload throttling.

Emulates network with the given configuration for the session.

const win = new BrowserWindow()

// To emulate a GPRS connection with 50kbps throughput and 500 ms latency.
win.webContents.session.enableNetworkEmulation({
  latency: 500,
  downloadThroughput: 6400,
  uploadThroughput: 6400
})

// To emulate a network outage.
win.webContents.session.enableNetworkEmulation({ offline: true })

ses.preconnect(options)

• options Object
  • url string - URL for preconnect. Only the origin is relevant for opening the socket.
  • numSockets number (optional) - number of sockets to preconnect. Must be between 1 and 6. Defaults to 1.

Preconnects the given number of sockets to an origin.

ses.closeAllConnections()

Returns Promise<void> - Resolves when all connections are closed.

Note: It will terminate / fail all requests currently in flight.

ses.fetch(input[, init])

• input string | GlobalRequest
• init RequestInit & { bypassCustomProtocolHandlers?: boolean } (optional)

Returns Promise<GlobalResponse> - see Response.

Sends a request, similarly to how fetch() works in the renderer, using Chrome's network stack. This differs from Node's fetch(), which uses Node.js's HTTP stack.

Example:

async function example () {
  const response = await net.fetch('https://my.app')
  if (response.ok) {
    const body = await response.json()
    // ... use the result.
  }
}

See also net.fetch(), a convenience method which issues requests from the default session.

See the MDN documentation for fetch() for more details.

Limitations:

• net.fetch() does not support the data: or blob: schemes.
• The value of the integrity option is ignored.
• The .type and .url values of the returned Response object are incorrect.

By default, requests made with net.fetch can be made to custom protocols as well as file:, and will trigger webRequest handlers if present. When the non-standard bypassCustomProtocolHandlers option is set in RequestInit, custom protocol handlers will not be called for this request. This allows forwarding an intercepted request to the built-in handler. webRequest handlers will still be triggered when bypassing custom protocols.

protocol.handle('https', (req) => {
  if (req.url === 'https://my-app.com') {
    return new Response('<body>my app</body>')
  } else {
    return net.fetch(req, { bypassCustomProtocolHandlers: true })
  }
})

ses.disableNetworkEmulation()

Disables any network emulation already active for the session. Resets to the original network configuration.

ses.setCertificateVerifyProc(proc)

• proc Function | null
  • request Object
    • hostname string
    • certificate Certificate
    • validatedCertificate Certificate
    • isIssuedByKnownRoot boolean - true if Chromium recognises the root CA as a standard root. If it isn't then it's probably the case that this certificate was generated by a MITM proxy whose root has been installed locally (for example, by a corporate proxy). This should not be trusted if the verificationResult is not OK.
    • verificationResult string - OK if the certificate is trusted, otherwise an error like CERT_REVOKED.
    • errorCode Integer - Error code.
  • callback Function
    • verificationResult Integer - Value can be one of certificate error codes from here. Apart from the certificate error codes, the following special codes can be used.
      • 0 - Indicates success and disables Certificate Transparency verification.
      • -2 - Indicates failure.
      • -3 - Uses the verification result from chromium.

Sets the certificate verify proc for session, the proc will be called with proc(request, callback) whenever a server certificate verification is requested. Calling callback(0) accepts the certificate, calling callback(-2) rejects it.

Calling setCertificateVerifyProc(null) will revert back to default certificate verify proc.

const { BrowserWindow } = require('electron')
const win = new BrowserWindow()

win.webContents.session.setCertificateVerifyProc((request, callback) => {
  const { hostname } = request
  if (hostname === 'github.com') {
    callback(0)
  } else {
    callback(-2)
  }
})

NOTE: The result of this procedure is cached by the network service.

ses.setPermissionRequestHandler(handler)

• handler Function | null
  • webContents WebContents - WebContents requesting the permission. Please note that if the request comes from a subframe you should use requestingUrl to check the request origin.
  • permission string - The type of requested permission.
    • clipboard-read - Request access to read from the clipboard.
    • clipboard-sanitized-write - Request access to write to the clipboard.
    • display-capture - Request access to capture the screen via the Screen Capture API.
    • fullscreen - Request control of the app's fullscreen state via the Fullscreen API.
    • geolocation - Request access to the user's location via the Geolocation API
    • idle-detection - Request access to the user's idle state via the IdleDetector API.
    • media - Request access to media devices such as camera, microphone and speakers.
    • mediaKeySystem - Request access to DRM protected content.
    • midi - Request MIDI access in the Web MIDI API.
    • midiSysex - Request the use of system exclusive messages in the Web MIDI API.
    • notifications - Request notification creation and the ability to display them in the user's system tray using the Notifications API
    • pointerLock - Request to directly interpret mouse movements as an input method via the Pointer Lock API. These requests always appear to originate from the main frame.
    • keyboardLock - Request capture of keypresses for any or all of the keys on the physical keyboard via the Keyboard Lock API. These requests always appear to originate from the main frame.
    • openExternal - Request to open links in external applications.
    • speaker-selection - Request to enumerate and select audio output devices via the speaker-selection permissions policy.
    • storage-access - Allows content loaded in a third-party context to request access to third-party cookies using the Storage Access API.
    • top-level-storage-access - Allow top-level sites to request third-party cookie access on behalf of embedded content originating from another site in the same related website set using the Storage Access API.
    • window-management - Request access to enumerate screens using the getScreenDetails API.
    • unknown - An unrecognized permission request.
    • fileSystem - Request access to read, write, and file management capabilities using the File System API.
  • callback Function
    • permissionGranted boolean - Allow or deny the permission.
  • details PermissionRequest | FilesystemPermissionRequest | MediaAccessPermissionRequest | OpenExternalPermissionRequest - Additional information about the permission being requested.

Sets the handler which can be used to respond to permission requests for the session. Calling callback(true) will allow the permission and callback(false) will reject it. To clear the handler, call setPermissionRequestHandler(null). Please note that you must also implement setPermissionCheckHandler to get complete permission handling. Most web APIs do a permission check and then make a permission request if the check is denied.

const { session } = require('electron')
session.fromPartition('some-partition').setPermissionRequestHandler((webContents, permission, callback) => {
  if (webContents.getURL() === 'some-host' && permission === 'notifications') {
    return callback(false) // denied.
  }

  callback(true)
})

ses.setPermissionCheckHandler(handler)

• handler Function<boolean> | null
  • webContents (WebContents | null) - WebContents checking the permission. Please note that if the request comes from a subframe you should use requestingUrl to check the request origin. All cross origin sub frames making permission checks will pass a null webContents to this handler, while certain other permission checks such as notifications checks will always pass null. You should use embeddingOrigin and requestingOrigin to determine what origin the owning frame and the requesting frame are on respectively.
  • permission string - Type of permission check.
    • clipboard-read - Request access to read from the clipboard.
    • clipboard-sanitized-write - Request access to write to the clipboard.
    • geolocation - Access the user's geolocation data via the Geolocation API
    • fullscreen - Control of the app's fullscreen state via the Fullscreen API.
    • hid - Access the HID protocol to manipulate HID devices via the WebHID API.
    • idle-detection - Access the user's idle state via the IdleDetector API.
    • media - Access to media devices such as camera, microphone and speakers.
    • mediaKeySystem - Access to DRM protected content.
    • midi - Enable MIDI access in the Web MIDI API.
    • midiSysex - Use system exclusive messages in the Web MIDI API.
    • notifications - Configure and display desktop notifications to the user with the Notifications API.
    • openExternal - Open links in external applications.
    • pointerLock - Directly interpret mouse movements as an input method via the Pointer Lock API. These requests always appear to originate from the main frame.
    • serial - Read from and write to serial devices with the Web Serial API.
    • storage-access - Allows content loaded in a third-party context to request access to third-party cookies using the Storage Access API.
    • top-level-storage-access - Allow top-level sites to request third-party cookie access on behalf of embedded content originating from another site in the same related website set using the Storage Access API.
    • usb - Expose non-standard Universal Serial Bus (USB) compatible devices services to the web with the WebUSB API.
  • requestingOrigin string - The origin URL of the permission check
  • details Object - Some properties are only available on certain permission types.
    • embeddingOrigin string (optional) - The origin of the frame embedding the frame that made the permission check. Only set for cross-origin sub frames making permission checks.
    • securityOrigin string (optional) - The security origin of the media check.
    • mediaType string (optional) - The type of media access being requested, can be video, audio or unknown
    • requestingUrl string (optional) - The last URL the requesting frame loaded. This is not provided for cross-origin sub frames making permission checks.
    • isMainFrame boolean - Whether the frame making the request is the main frame

Sets the handler which can be used to respond to permission checks for the session. Returning true will allow the permission and false will reject it. Please note that you must also implement setPermissionRequestHandler to get complete permission handling. Most web APIs do a permission check and then make a permission request if the check is denied. To clear the handler, call setPermissionCheckHandler(null).

const { session } = require('electron')
const url = require('url')
session.fromPartition('some-partition').setPermissionCheckHandler((webContents, permission, requestingOrigin) => {
  if (new URL(requestingOrigin).hostname === 'some-host' && permission === 'notifications') {
    return true // granted
  }

  return false // denied
})

ses.setDisplayMediaRequestHandler(handler)

• handler Function | null
  • request Object
    • frame WebFrameMain - Frame that is requesting access to media.
    • securityOrigin String - Origin of the page making the request.
    • videoRequested Boolean - true if the web content requested a video stream.
    • audioRequested Boolean - true if the web content requested an audio stream.
    • userGesture Boolean - Whether a user gesture was active when this request was triggered.
  • callback Function
    • streams Object
      • video Object | WebFrameMain (optional)
        • id String - The id of the stream being granted. This will usually come from a DesktopCapturerSource object.
        • name String - The name of the stream being granted. This will usually come from a DesktopCapturerSource object.
      • audio String | WebFrameMain (optional) - If a string is specified, can be loopback or loopbackWithMute. Specifying a loopback device will capture system audio, and is currently only supported on Windows. If a WebFrameMain is specified, will capture audio from that frame.
      • enableLocalEcho Boolean (optional) - If audio is a WebFrameMain and this is set to true, then local playback of audio will not be muted (e.g. using MediaRecorder to record WebFrameMain with this flag set to true will allow audio to pass through to the speakers while recording). Default is false.

This handler will be called when web content requests access to display media via the navigator.mediaDevices.getDisplayMedia API. Use the desktopCapturer API to choose which stream(s) to grant access to.

const { session, desktopCapturer } = require('electron')

session.defaultSession.setDisplayMediaRequestHandler((request, callback) => {
  desktopCapturer.getSources({ types: ['screen'] }).then((sources) => {
    // Grant access to the first screen found.
    callback({ video: sources[0] })
  })
})

Passing a WebFrameMain object as a video or audio stream will capture the video or audio stream from that frame.

const { session } = require('electron')

session.defaultSession.setDisplayMediaRequestHandler((request, callback) => {
  // Allow the tab to capture itself.
  callback({ video: request.frame })
})

Passing null instead of a function resets the handler to its default state.

ses.setDevicePermissionHandler(handler)

• handler Function<boolean> | null
  • details Object
    • deviceType string - The type of device that permission is being requested on, can be hid, serial, or usb.
    • origin string - The origin URL of the device permission check.
    • device HIDDevice | SerialPort | USBDevice - the device that permission is being requested for.

Sets the handler which can be used to respond to device permission checks for the session. Returning true will allow the device to be permitted and false will reject it. To clear the handler, call setDevicePermissionHandler(null). This handler can be used to provide default permissioning to devices without first calling for permission to devices (eg via navigator.hid.requestDevice). If this handler is not defined, the default device permissions as granted through device selection (eg via navigator.hid.requestDevice) will be used. Additionally, the default behavior of Electron is to store granted device permission in memory. If longer term storage is needed, a developer can store granted device permissions (eg when handling the select-hid-device event) and then read from that storage with setDevicePermissionHandler.

const { app, BrowserWindow } = require('electron')

let win = null

app.whenReady().then(() => {
  win = new BrowserWindow()

  win.webContents.session.setPermissionCheckHandler((webContents, permission, requestingOrigin, details) => {
    if (permission === 'hid') {
      // Add logic here to determine if permission should be given to allow HID selection
      return true
    } else if (permission === 'serial') {
      // Add logic here to determine if permission should be given to allow serial port selection
    } else if (permission === 'usb') {
      // Add logic here to determine if permission should be given to allow USB device selection
    }
    return false
  })

  // Optionally, retrieve previously persisted devices from a persistent store
  const grantedDevices = fetchGrantedDevices()

  win.webContents.session.setDevicePermissionHandler((details) => {
    if (new URL(details.origin).hostname === 'some-host' && details.deviceType === 'hid') {
      if (details.device.vendorId === 123 && details.device.productId === 345) {
        // Always allow this type of device (this allows skipping the call to `navigator.hid.requestDevice` first)
        return true
      }

      // Search through the list of devices that have previously been granted permission
      return grantedDevices.some((grantedDevice) => {
        return grantedDevice.vendorId === details.device.vendorId &&
              grantedDevice.productId === details.device.productId &&
              grantedDevice.serialNumber && grantedDevice.serialNumber === details.device.serialNumber
      })
    } else if (details.deviceType === 'serial') {
      if (details.device.vendorId === 123 && details.device.productId === 345) {
        // Always allow this type of device (this allows skipping the call to `navigator.hid.requestDevice` first)
        return true
      }
    }
    return false
  })

  win.webContents.session.on('select-hid-device', (event, details, callback) => {
    event.preventDefault()
    const selectedDevice = details.deviceList.find((device) => {
      return device.vendorId === 9025 && device.productId === 67
    })
    callback(selectedDevice?.deviceId)
  })
})

ses.setUSBProtectedClassesHandler(handler)

• handler Function<string[]> | null
  • details Object
    • protectedClasses string[] - The current list of protected USB classes. Possible class values include:
      • audio
      • audio-video
      • hid
      • mass-storage
      • smart-card
      • video
      • wireless

Sets the handler which can be used to override which USB classes are protected. The return value for the handler is a string array of USB classes which should be considered protected (eg not available in the renderer). Valid values for the array are:

• audio
• audio-video
• hid
• mass-storage
• smart-card
• video
• wireless

Returning an empty string array from the handler will allow all USB classes; returning the passed in array will maintain the default list of protected USB classes (this is also the default behavior if a handler is not defined). To clear the handler, call setUSBProtectedClassesHandler(null).

const { app, BrowserWindow } = require('electron')

let win = null

app.whenReady().then(() => {
  win = new BrowserWindow()

  win.webContents.session.setUSBProtectedClassesHandler((details) => {
    // Allow all classes:
    // return []
    // Keep the current set of protected classes:
    // return details.protectedClasses
    // Selectively remove classes:
    return details.protectedClasses.filter((usbClass) => {
      // Exclude classes except for audio classes
      return usbClass.indexOf('audio') === -1
    })
  })
})

ses.setBluetoothPairingHandler(handler) Windows Linux

• handler Function | null
  • details Object
    • deviceId string
    • pairingKind string - The type of pairing prompt being requested. One of the following values:
      • confirm This prompt is requesting confirmation that the Bluetooth device should be paired.
      • confirmPin This prompt is requesting confirmation that the provided PIN matches the pin displayed on the device.
      • providePin This prompt is requesting that a pin be provided for the device.
    • frame WebFrameMain
    • pin string (optional) - The pin value to verify if pairingKind is confirmPin.
  • callback Function
    • response Object
      • confirmed boolean - false should be passed in if the dialog is canceled. If the pairingKind is confirm or confirmPin, this value should indicate if the pairing is confirmed. If the pairingKind is providePin the value should be true when a value is provided.
      • pin string | null (optional) - When the pairingKind is providePin this value should be the required pin for the Bluetooth device.

Sets a handler to respond to Bluetooth pairing requests. This handler allows developers to handle devices that require additional validation before pairing. When a handler is not defined, any pairing on Linux or Windows that requires additional validation will be automatically cancelled. macOS does not require a handler because macOS handles the pairing automatically. To clear the handler, call setBluetoothPairingHandler(null).

const { app, BrowserWindow, session } = require('electron')
const path = require('node:path')

function createWindow () {
  let bluetoothPinCallback = null

  const mainWindow = new BrowserWindow({
    webPreferences: {
      preload: path.join(__dirname, 'preload.js')
    }
  })

  mainWindow.webContents.session.setBluetoothPairingHandler((details, callback) => {
    bluetoothPinCallback = callback
    // Send a IPC message to the renderer to prompt the user to confirm the pairing.
    // Note that this will require logic in the renderer to handle this message and
    // display a prompt to the user.
    mainWindow.webContents.send('bluetooth-pairing-request', details)
  })

  // Listen for an IPC message from the renderer to get the response for the Bluetooth pairing.
  mainWindow.webContents.ipc.on('bluetooth-pairing-response', (event, response) => {
    bluetoothPinCallback(response)
  })
}

app.whenReady().then(() => {
  createWindow()
})

ses.clearHostResolverCache()

Returns Promise<void> - Resolves when the operation is complete.

Clears the host resolver cache.

ses.allowNTLMCredentialsForDomains(domains)

• domains string - A comma-separated list of servers for which integrated authentication is enabled.

Dynamically sets whether to always send credentials for HTTP NTLM or Negotiate authentication.

const { session } = require('electron')
// consider any url ending with `example.com`, `foobar.com`, `baz`
// for integrated authentication.
session.defaultSession.allowNTLMCredentialsForDomains('*example.com, *foobar.com, *baz')

// consider all urls for integrated authentication.
session.defaultSession.allowNTLMCredentialsForDomains('*')

ses.setUserAgent(userAgent[, acceptLanguages])

• userAgent string
• acceptLanguages string (optional)

Overrides the userAgent and acceptLanguages for this session.

The acceptLanguages must a comma separated ordered list of language codes, for example "en-US,fr,de,ko,zh-CN,ja".

This doesn't affect existing WebContents, and each WebContents can use webContents.setUserAgent to override the session-wide user agent.

ses.isPersistent()

Returns boolean - Whether or not this session is a persistent one. The default webContents session of a BrowserWindow is persistent. When creating a session from a partition, session prefixed with persist: will be persistent, while others will be temporary.

ses.getUserAgent()

Returns string - The user agent for this session.

ses.setSSLConfig(config)

• config Object
  • minVersion string (optional) - Can be tls1, tls1.1, tls1.2 or tls1.3. The minimum SSL version to allow when connecting to remote servers. Defaults to tls1.
  • maxVersion string (optional) - Can be tls1.2 or tls1.3. The maximum SSL version to allow when connecting to remote servers. Defaults to tls1.3.
  • disabledCipherSuites Integer[] (optional) - List of cipher suites which should be explicitly prevented from being used in addition to those disabled by the net built-in policy. Supported literal forms: 0xAABB, where AA is cipher_suite[0] and BB is cipher_suite[1], as defined in RFC 2246, Section 7.4.1.2. Unrecognized but parsable cipher suites in this form will not return an error. Ex: To disable TLS_RSA_WITH_RC4_128_MD5, specify 0x0004, while to disable TLS_ECDH_ECDSA_WITH_RC4_128_SHA, specify 0xC002. Note that TLSv1.3 ciphers cannot be disabled using this mechanism.

Sets the SSL configuration for the session. All subsequent network requests will use the new configuration. Existing network connections (such as WebSocket connections) will not be terminated, but old sockets in the pool will not be reused for new connections.

ses.getBlobData(identifier)

• identifier string - Valid UUID.

Returns Promise<Buffer> - resolves with blob data.

ses.downloadURL(url[, options])

• url string
• options Object (optional)
  • headers Record<string, string> (optional) - HTTP request headers.

Initiates a download of the resource at url. The API will generate a DownloadItem that can be accessed with the will-download event.

Note: This does not perform any security checks that relate to a page's origin, unlike webContents.downloadURL.

ses.createInterruptedDownload(options)

• options Object
  • path string - Absolute path of the download.
  • urlChain string[] - Complete URL chain for the download.
  • mimeType string (optional)
  • offset Integer - Start range for the download.
  • length Integer - Total length of the download.
  • lastModified string (optional) - Last-Modified header value.
  • eTag string (optional) - ETag header value.
  • startTime Double (optional) - Time when download was started in number of seconds since UNIX epoch.

Allows resuming cancelled or interrupted downloads from previous Session. The API will generate a DownloadItem that can be accessed with the will-download event. The DownloadItem will not have any WebContents associated with it and the initial state will be interrupted. The download will start only when the resume API is called on the DownloadItem.

ses.clearAuthCache()

Returns Promise<void> - resolves when the session’s HTTP authentication cache has been cleared.

ses.setPreloads(preloads)

• preloads string[] - An array of absolute path to preload scripts

Adds scripts that will be executed on ALL web contents that are associated with this session just before normal preload scripts run.

ses.getPreloads()

Returns string[] an array of paths to preload scripts that have been registered.

ses.setCodeCachePath(path)

• path String - Absolute path to store the v8 generated JS code cache from the renderer.

Sets the directory to store the generated JS code cache for this session. The directory is not required to be created by the user before this call, the runtime will create if it does not exist otherwise will use the existing directory. If directory cannot be created, then code cache will not be used and all operations related to code cache will fail silently inside the runtime. By default, the directory will be Code Cache under the respective user data folder.

Note that by default code cache is only enabled for http(s) URLs, to enable code cache for custom protocols, codeCache: true and standard: true must be specified when registering the protocol.

ses.clearCodeCaches(options)

• options Object
  • urls String[] (optional) - An array of url corresponding to the resource whose generated code cache needs to be removed. If the list is empty then all entries in the cache directory will be removed.

Returns Promise<void> - resolves when the code cache clear operation is complete.

ses.setSpellCheckerEnabled(enable)

• enable boolean

Sets whether to enable the builtin spell checker.

ses.isSpellCheckerEnabled()

Returns boolean - Whether the builtin spell checker is enabled.

ses.setSpellCheckerLanguages(languages)

• languages string[] - An array of language codes to enable the spellchecker for.

The built in spellchecker does not automatically detect what language a user is typing in. In order for the spell checker to correctly check their words you must call this API with an array of language codes. You can get the list of supported language codes with the ses.availableSpellCheckerLanguages property.

Note: On macOS the OS spellchecker is used and will detect your language automatically. This API is a no-op on macOS.

ses.getSpellCheckerLanguages()

Returns string[] - An array of language codes the spellchecker is enabled for. If this list is empty the spellchecker will fallback to using en-US. By default on launch if this setting is an empty list Electron will try to populate this setting with the current OS locale. This setting is persisted across restarts.

Note: On macOS the OS spellchecker is used and has its own list of languages. On macOS, this API will return whichever languages have been configured by the OS.

ses.setSpellCheckerDictionaryDownloadURL(url)

• url string - A base URL for Electron to download hunspell dictionaries from.

By default Electron will download hunspell dictionaries from the Chromium CDN. If you want to override this behavior you can use this API to point the dictionary downloader at your own hosted version of the hunspell dictionaries. We publish a hunspell_dictionaries.zip file with each release which contains the files you need to host here.

The file server must be case insensitive. If you cannot do this, you must upload each file twice: once with the case it has in the ZIP file and once with the filename as all lowercase.

If the files present in hunspell_dictionaries.zip are available at https://example.com/dictionaries/language-code.bdic then you should call this api with ses.setSpellCheckerDictionaryDownloadURL('https://example.com/dictionaries/'). Please note the trailing slash. The URL to the dictionaries is formed as ${url}${filename}.

Note: On macOS the OS spellchecker is used and therefore we do not download any dictionary files. This API is a no-op on macOS.

ses.listWordsInSpellCheckerDictionary()

Returns Promise<string[]> - An array of all words in app's custom dictionary. Resolves when the full dictionary is loaded from disk.

ses.addWordToSpellCheckerDictionary(word)

• word string - The word you want to add to the dictionary

Returns boolean - Whether the word was successfully written to the custom dictionary. This API will not work on non-persistent (in-memory) sessions.

Note: On macOS and Windows 10 this word will be written to the OS custom dictionary as well

ses.removeWordFromSpellCheckerDictionary(word)

• word string - The word you want to remove from the dictionary

Returns boolean - Whether the word was successfully removed from the custom dictionary. This API will not work on non-persistent (in-memory) sessions.

Note: On macOS and Windows 10 this word will be removed from the OS custom dictionary as well

ses.loadExtension(path[, options])

• path string - Path to a directory containing an unpacked Chrome extension
• options Object (optional)
  • allowFileAccess boolean - Whether to allow the extension to read local files over file:// protocol and inject content scripts into file:// pages. This is required e.g. for loading devtools extensions on file:// URLs. Defaults to false.

Returns Promise<Extension> - resolves when the extension is loaded.

This method will raise an exception if the extension could not be loaded. If there are warnings when installing the extension (e.g. if the extension requests an API that Electron does not support) then they will be logged to the console.

Note that Electron does not support the full range of Chrome extensions APIs. See Supported Extensions APIs for more details on what is supported.

Note that in previous versions of Electron, extensions that were loaded would be remembered for future runs of the application. This is no longer the case: loadExtension must be called on every boot of your app if you want the extension to be loaded.

const { app, session } = require('electron')
const path = require('node:path')

app.whenReady().then(async () => {
  await session.defaultSession.loadExtension(
    path.join(__dirname, 'react-devtools'),
    // allowFileAccess is required to load the devtools extension on file:// URLs.
    { allowFileAccess: true }
  )
  // Note that in order to use the React DevTools extension, you'll need to
  // download and unzip a copy of the extension.
})

This API does not support loading packed (.crx) extensions.

Note: This API cannot be called before the ready event of the app module is emitted.

Note: Loading extensions into in-memory (non-persistent) sessions is not supported and will throw an error.

ses.removeExtension(extensionId)

• extensionId string - ID of extension to remove

Unloads an extension.

Note: This API cannot be called before the ready event of the app module is emitted.

ses.getExtension(extensionId)

• extensionId string - ID of extension to query

Returns Extension | null - The loaded extension with the given ID.

Note: This API cannot be called before the ready event of the app module is emitted.

ses.getAllExtensions()

Returns Extension[] - A list of all loaded extensions.

Note: This API cannot be called before the ready event of the app module is emitted.

ses.getStoragePath()

Returns string | null - The absolute file system path where data for this session is persisted on disk. For in memory sessions this returns null.

ses.clearData([options])

• options Object (optional)
  • dataTypes String[] (optional) - The types of data to clear. By default, this will clear all types of data.
    • backgroundFetch - Background Fetch
    • cache - Cache
    • cookies - Cookies
    • downloads - Downloads
    • fileSystems - File Systems
    • indexedDB - IndexedDB
    • localStorage - Local Storage
    • serviceWorkers - Service Workers
    • webSQL - WebSQL
  • origins String[] (optional) - Clear data for only these origins. Cannot be used with excludeOrigins.
  • excludeOrigins String[] (optional) - Clear data for all origins except these ones. Cannot be used with origins.
  • avoidClosingConnections boolean (optional) - Skips deleting cookies that would close current network connections. (Default: false)
  • originMatchingMode String (optional) - The behavior for matching data to origins.
    • third-parties-included (default) - Storage is matched on origin in first-party contexts and top-level-site in third-party contexts.
    • origin-in-all-contexts - Storage is matched on origin only in all contexts.

Returns Promise<void> - resolves when all data has been cleared.

Clears various different types of data.

This method clears more types of data and is more thorough than the clearStorageData method.

Note: Cookies are stored at a broader scope than origins. When removing cookies and filtering by origins (or excludeOrigins), the cookies will be removed at the registrable domain level. For example, clearing cookies for the origin https://really.specific.origin.example.com/ will end up clearing all cookies for example.com. Clearing cookies for the origin https://my.website.example.co.uk/ will end up clearing all cookies for example.co.uk.

For more information, refer to Chromium's BrowsingDataRemover interface.

Instance Properties

The following properties are available on instances of Session:

ses.availableSpellCheckerLanguages Readonly

A string[] array which consists of all the known available spell checker languages. Providing a language code to the setSpellCheckerLanguages API that isn't in this array will result in an error.

ses.spellCheckerEnabled

A boolean indicating whether builtin spell checker is enabled.

ses.storagePath Readonly

A string | null indicating the absolute file system path where data for this session is persisted on disk. For in memory sessions this returns null.

ses.cookies Readonly

A Cookies object for this session.

ses.serviceWorkers Readonly

A ServiceWorkers object for this session.

ses.webRequest Readonly

A WebRequest object for this session.

ses.protocol Readonly

A Protocol object for this session.

const { app, session } = require('electron')
const path = require('node:path')

app.whenReady().then(() => {
  const protocol = session.fromPartition('some-partition').protocol
  if (!protocol.registerFileProtocol('atom', (request, callback) => {
    const url = request.url.substr(7)
    callback({ path: path.normalize(path.join(__dirname, url)) })
  })) {
    console.error('Failed to register protocol')
  }
})

ses.netLog Readonly

A NetLog object for this session.

const { app, session } = require('electron')

app.whenReady().then(async () => {
  const netLog = session.fromPartition('some-partition').netLog
  netLog.startLogging('/path/to/net-log')
  // After some network events
  const path = await netLog.stopLogging()
  console.log('Net-logs written to', path)
})