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('http://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.

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

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('request')(item.getURL(), (data) => {
    require('fs').writeFileSync('/somewhere', data)
  })
})

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: '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-serial-port' Experimental

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.

Because this is an experimental feature it is disabled by default. To enable this feature, you will need to use the --enable-features=ElectronSerialChooser command line switch. Additionally because this is an experimental Chromium feature you will need to set enableBlinkFeatures: 'Serial' on the webPreferences property when opening a BrowserWindow.

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

let win = null
app.commandLine.appendSwitch('enable-features', 'ElectronSerialChooser')

app.whenReady().then(() => {
  win = new BrowserWindow({
    width: 800,
    height: 600,
    webPreferences: {
      enableBlinkFeatures: 'Serial'
    }
  })
  win.webContents.session.on('select-serial-port', (event, portList, callback) => {
    event.preventDefault()
    const selectedPort = portList.find((device) => {
      return device.vendorId === 0x2341 && device.productId === 0x0043
    })
    if (!selectedPort) {
      callback('')
    } else {
      callback(result1.portId)
    }
  })
})

Event: 'serial-port-added' Experimental

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. For example, this event will fire when a new USB device is plugged in.

Event: 'serial-port-removed' Experimental

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. For example, this event will fire when a USB device is unplugged.

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 contain: appcache, 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 contain: temporary, persistent, 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 Object
  • pacScript String (optional) - The URL associated with the PAC file.
  • proxyRules String (optional) - Rules indicating which proxies to use.
  • proxyBypassRules String (optional) - Rules indicating which URLs should bypass the proxy settings.

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

Sets the proxy settings.

When pacScript and proxyRules are provided together, the proxyRules option is ignored and pacScript configuration is applied.

The proxyRules has to follow the rules below:

proxyRules = schemeProxies[";"<schemeProxies>]
schemeProxies = [<urlScheme>"="]<proxyURIList>
urlScheme = "http" | "https" | "ftp" | "socks"
proxyURIList = <proxyURL>[","<proxyURIList>]
proxyURL = [<proxyScheme>"://"]<proxyHost>[":"<proxyPort>]

For example:

• http=foopy:80;ftp=foopy2 - Use HTTP proxy foopy:80 for http:// URLs, and HTTP proxy foopy2:80 for ftp:// URLs.
• foopy:80 - Use HTTP proxy foopy:80 for all URLs.
• foopy:80,bar,direct:// - Use HTTP proxy foopy:80 for all URLs, failing over to bar if foopy:80 is unavailable, and after that using no proxy.
• socks4://foopy - Use SOCKS v4 proxy foopy:1080 for all URLs.
• http=foopy,socks5://bar.com - Use HTTP proxy foopy for http URLs, and fail over to the SOCKS5 proxy bar.com if foopy is unavailable.
• http=foopy,direct:// - Use HTTP proxy foopy for http URLs, and use no proxy if foopy is unavailable.
• http=foopy;socks=foopy2 - Use HTTP proxy foopy for http URLs, and use socks4://foopy2 for all other URLs.

The proxyBypassRules is a comma separated list of rules described below:

• [ URL_SCHEME "://" ] HOSTNAME_PATTERN [ ":" <port> ]

  Match all hostnames that match the pattern HOSTNAME_PATTERN.

  Examples: "foobar.com", "foobar.com", ".foobar.com", "foobar.com:99", "https://x..y.com:99"

• "." HOSTNAME_SUFFIX_PATTERN [ ":" PORT ]

  Match a particular domain suffix.

  Examples: ".google.com", ".com", "http://.google.com"

• [ SCHEME "://" ] IP_LITERAL [ ":" PORT ]

  Match URLs which are IP address literals.

  Examples: "127.0.1", "[0:0::1]", "[::1]", "http://[::1]:99"

• IP_LITERAL "/" PREFIX_LENGTH_IN_BITS

  Match any URL that is to an IP literal that falls between the given range. IP range is specified using CIDR notation.

  Examples: "192.168.1.1/16", "fefe:13::abc/33".

• <local>

  Match local addresses. The meaning of <local> is whether the host matches one of: "127.0.0.1", "::1", "localhost".

ses.resolveProxy(url)

• url URL

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

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.

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

// To emulate a network outage.
window.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.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
    • verificationResult String - Verification result from chromium.
    • 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)
  }
})

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.
    • media - Request access to media devices such as camera, microphone and speakers.
    • mediaKeySystem - Request access to DRM protected content.
    • geolocation - Request access to user's current location.
    • notifications - Request notification creation and the ability to display them in the user's system tray.
    • midi - Request MIDI access in the webmidi API.
    • midiSysex - Request the use of system exclusive messages in the webmidi API.
    • pointerLock - Request to directly interpret mouse movements as an input method. Click here to know more.
    • fullscreen - Request for the app to enter fullscreen mode.
    • openExternal - Request to open links in external applications.
  • callback Function
    • permissionGranted Boolean - Allow or deny the permission.
  • details Object - Some properties are only available on certain permission types.
    • externalURL String (optional) - The url of the openExternal request.
    • mediaTypes String[] (optional) - The types of media access being requested, elements can be video or audio
    • requestingUrl String - The last URL the requesting frame loaded
    • isMainFrame Boolean - Whether the frame making the request is the main frame

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).

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 | null
  • webContents WebContents - WebContents checking the permission. Please note that if the request comes from a subframe you should use requestingUrl to check the request origin.
  • permission String - Type of permission check. Valid values are midiSysex, notifications, geolocation, media,mediaKeySystem,midi, pointerLock, fullscreen, openExternal, or serial.
  • requestingOrigin String - The origin URL of the permission check
  • details Object - Some properties are only available on certain permission types.
    • securityOrigin String - The security origin of the media check.
    • mediaType String - The type of media access being requested, can be video, audio or unknown
    • requestingUrl String - The last URL the requesting frame loaded
    • 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. To clear the handler, call setPermissionCheckHandler(null).

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

  return true
})

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 - 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 - Can be tls1.2 or tls1.3. The maximum SSL version to allow when connecting to remote servers. Defaults to tls1.3.

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)

• url String

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.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. This API is a no-op on macOS.

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 you must upload each file twice, once with the case it has in the ZIP file and once with the filename as all lower case.

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)

• path String - Path to a directory containing an unpacked Chrome extension

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('path')

app.on('ready', async () => {
  await session.defaultSession.loadExtension(path.join(__dirname, 'react-devtools'))
  // 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.

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 setSpellCheckerLanaguages API that isn't in this array will result in an error.

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('path')

app.whenReady().then(() => {
  const protocol = session.fromPartition('some-partition').protocol
  protocol.registerFileProtocol('atom', (request, callback) => {
    const url = request.url.substr(7)
    callback({ path: path.normalize(`${__dirname}/${url}`) })
  }, (error) => {
    if (error) 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)
})