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')

let win = new BrowserWindow({width: 800, height: 600})

const ses = win.webContents.session


The session module has the following methods:

session.fromPartition(partition[, options])

  • partition String
  • options Object
    • 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.

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')

Instance Events

The following events are available on instances of Session:

Event: 'will-download'

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

Instance Methods

The following methods are available on instances of Session:


  • callback Function
    • size Integer - Cache size used in bytes.

Callback is invoked with the session's current cache size.


  • callback Function - Called when operation is done

Clears the session’s HTTP cache.

ses.clearStorageData([options, callback])

  • options Object (optional)
    • origin String - Should follow window.location.origin’s representation scheme://host:port.
    • storages String[] - The types of storages to clear, can contain: appcache, cookies, filesystem, indexdb, localstorage, shadercache, websql, serviceworkers
    • quotas String[] - The types of quotas to clear, can contain: temporary, persistent, syncable.
  • callback Function (optional) - Called when operation is done.

Clears the data of web storages.


Writes any unwritten DOMStorage data to disk.

ses.setProxy(config, callback)

  • config Object
    • pacScript String - The URL associated with the PAC file.
    • proxyRules String - Rules indicating which proxies to use.
    • proxyBypassRules String - Rules indicating which URLs should bypass the proxy settings.
  • callback Function - Called when operation is done.

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:// - Use HTTP proxy foopy for http URLs, and fail over to the SOCKS5 proxy 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: "", "", "", "", ""


      Match a particular domain suffix.

      Examples: "", ".com", ""

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

    Match URLs which are IP address literals.

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


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

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

  • <local>

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

ses.resolveProxy(url, callback)

  • url URL
  • callback Function
    • proxy String

Resolves the proxy information for url. The callback will be called with callback(proxy) when the request is performed.


  • path String - The download location

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


  • 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.
  latency: 500,
  downloadThroughput: 6400,
  uploadThroughput: 6400

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


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


  • proc Function
    • request Object
      • hostname String
      • certificate Certificate
      • error String - Verification result from chromium.
    • 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 Transperancy 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')
let win = new BrowserWindow()

win.webContents.session.setCertificateVerifyProc((request, callback) => {
  const {hostname} = request
  if (hostname === '') {
  } else {


  • handler Function
    • webContents Object - WebContents requesting the permission.
    • permission String - Enum of 'media', 'geolocation', 'notifications', 'midiSysex', 'pointerLock', 'fullscreen', 'openExternal'.
    • callback Function
      • permissionGranted Boolean - Allow or deny the permission

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.

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



  • callback Function (optional) - Called when operation is done.

Clears the host resolver cache.


  • domains String - A comma-seperated 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 ``, ``, `baz`
// for integrated authentication.
session.defaultSession.allowNTLMCredentialsForDomains('*, *, *baz')

// consider all urls for integrated authentication.

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.


Returns String - The user agent for this session.

ses.getBlobData(identifier, callback)

  • identifier String - Valid UUID.
  • callback Function
    • result Buffer - Blob data.

Returns Blob - The blob data associated with the identifier.


  • 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 - Last-Modified header value.
    • eTag String - 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(options[, callback])

Clears the session’s HTTP authentication cache.

Instance Properties

The following properties are available on instances of Session:


A Cookies object for this session.


A WebRequest object for this session.


A Protocol object (an instance of protocol module) for this session.

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

app.on('ready', function () {
  const protocol = session.fromPartition('some-partition').protocol
  protocol.registerFileProtocol('atom', function (request, callback) {
    var url = request.url.substr(7)
    callback({path: path.normalize(`${__dirname}/${url}`)})
  }, function (error) {
    if (error) console.error('Failed to register protocol')

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