session

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 , or from the session module.

The session module has the following methods:

• 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.

The session module has the following properties:

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

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())

The following events are available on instances of Session:

Event: ‘will-download’

Returns:

• event Event
• item DownloadItem
• 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('fs').writeFileSync('/somewhere', response.body)
  })
})

Event: ‘extension-loaded’

Returns:

• event Event
• 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 .

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
  • 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 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(selectedPort?.deviceId)
  })
})

Event: ‘hid-device-added’

Returns:

• event Event
• details Object
  • device HIDDevice[]
  • frame

Emitted when a new HID device becomes available. For example, when a new USB device is plugged in.

This event will only be emitted after navigator.hid.requestDevice has been called and select-hid-device has fired.

Event: ‘hid-device-removed’

Returns:

• event Event
• details Object
  • device
  • frame WebFrameMain

Emitted when a HID device has been removed. For example, this event will fire when a USB device is unplugged.

This event will only be emitted after navigator.hid.requestDevice has been called and select-hid-device has fired.

Event: ‘select-serial-port’

Returns:

• event Event
• portList SerialPort[]
• 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

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’

Returns:

• event Event
• port
• 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.

The following methods are available on instances of Session:

ses.getCacheSize()

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
  • mode string (optional) - The proxy mode. Should be one of direct, auto_detect, pac_script, fixed_servers or system. If it’s unspecified, it will be automatically determined based on other specified options.
    • direct In direct mode all connections are created directly, without any proxy involved.
    • auto_detect In auto_detect mode the proxy configuration is determined by a PAC script that can be downloaded at http://wpad/wpad.dat.
    • pac_script In pac_script mode the proxy configuration is determined by a PAC script that is retrieved from the URL specified in the pacScript. This is the default mode if pacScript is specified.
    • fixed_servers In fixed_servers mode the proxy configuration is specified in proxyRules. This is the default mode if proxyRules is specified.
    • system In system mode the proxy configuration is taken from the operating system. Note that the system mode is different from setting no proxy configuration. In the latter case, Electron falls back to the system settings only if no command-line options influence the proxy configuration.
  • 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 mode is unspecified, pacScript and proxyRules are provided together, the proxyRules option is ignored and pacScript configuration is applied.

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

The proxyRules has to follow the rules below:

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”, ““

• [ 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.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.

// 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.closeAllConnections()

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

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

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
    • 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

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.
    • clipboard-read - Request access to read from the clipboard.
    • media - Request access to media devices such as camera, microphone and speakers.
    • display-capture - Request access to capture the screen.
    • 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 to know more.
    • fullscreen - Request for the app to enter fullscreen mode.
    • openExternal - Request to open links in external applications.
    • unknown - An unrecognized permission request
  • 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.
    • securityOrigin string (optional) - The security origin of the media 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). 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\ | null
  • 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. Valid values are midiSysex, , geolocation, media,mediaKeySystem,midi, pointerLock, fullscreen, openExternal, hid, or serial.
  • 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.setDevicePermissionHandler(handler)

• handler Function\ | null
  • details Object
    • deviceType string - The type of device that permission is being requested on, can be hid or serial.
    • origin string - The origin URL of the device permission check.
    • device | SerialPort- the device that permission is being requested for.
    • frame - WebFrameMain checking the device permission.

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 permision through the lifetime of the corresponding WebContents. 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.

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.

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 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 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 .

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.

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. 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. 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 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'),
    // 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()

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.

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('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(`${__dirname}/${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)