electron/docs/api/session.md

# session

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

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`](web-contents.md), or from the `session` module.

```javascript
const {session, BrowserWindow} = require('electron')

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

const ses = win.webContents.session
```

## Methods

The `session` module has the following methods:

### session.fromPartition(partition[, options])

* `partition` String
* `options` Object
  * `cache` Boolean - Whether to enable cache.

Returns a `Session` instance from `partition` string. When there is an existing
`Session` with the same `partition`, it will be returned; othewise 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

Returns the default session object of the app.

## Class: Session

You can create a `Session` object in the `session` module:

```javascript
const session = require('electron').session;

const ses = session.fromPartition('persist:name');
```

### Instance Events

The following events are available on instances of `Session`:

#### Event: 'will-download'

* `event` Event
* `item` [DownloadItem](download-item.md)
* `webContents` [WebContents](web-contents.md)

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.

```javascript
session.defaultSession.on('will-download', (event, item, webContents) => {
  event.preventDefault();
  require('request')(item.getURL(), (data) => {
    require('fs').writeFileSync('/somewhere', data);
  });
});
```

### Instance Methods

The following methods are available on instances of `Session`:

#### `ses.getCacheSize(callback)`

* `callback` Function
  * `size` Integer - Cache size used in bytes.

Returns the session's current cache size.

#### `ses.clearCache(callback)`

* `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` Array - The types of storages to clear, can contain:
    `appcache`, `cookies`, `filesystem`, `indexdb`, `local storage`,
    `shadercache`, `websql`, `serviceworkers`
  * `quotas` Array - The types of quotas to clear, can contain:
    `temporary`, `persistent`, `syncable`.
* `callback` Function - Called when operation is done.

Clears the data of web storages.

#### `ses.flushStorageData()`

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.
* `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://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.

### `ses.resolveProxy(url, callback)`

* `url` URL
* `callback` Function

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

#### `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 - Whether to emulate network outage.
  * `latency` Double - RTT in ms
  * `downloadThroughput` Double - Download rate in Bps
  * `uploadThroughput` Double - Upload rate in Bps

Emulates network with the given configuration for the `session`.

```javascript
// 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.disableNetworkEmulation()`

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

#### `ses.setCertificateVerifyProc(proc)`

* `proc` Function

Sets the certificate verify proc for `session`, the `proc` will be called with
`proc(hostname, certificate, callback)` whenever a server certificate
verification is requested. Calling `callback(true)` accepts the certificate,
calling `callback(false)` rejects it.

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

```javascript
myWindow.webContents.session.setCertificateVerifyProc((hostname, cert, callback) => {
  if (hostname === 'github.com')
    callback(true);
  else
    callback(false);
});
```

#### `ses.setPermissionRequestHandler(handler)`

* `handler` Function
  * `webContents` Object - [WebContents](web-contents.md) requesting the permission.
  * `permission` String - Enum of 'media', 'geolocation', 'notifications', 'midiSysex',
    'pointerLock', 'fullscreen', 'openExternal'.
  * `callback` Function - 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.

```javascript
session.fromPartition(partition).setPermissionRequestHandler((webContents, permission, callback) => {
  if (webContents.getURL() === host) {
    if (permission === 'notifications') {
      callback(false); // denied.
      return;
    }
  }

  callback(true);
});
```

#### `ses.clearHostResolverCache([callback])`

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

Clears the host resolver cache.

#### `ses.allowNTLMCredentialsForDomains(domains)`

* `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.

```javascript
// 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.getUserAgent()`

Returns a `String` representing the user agent for this session.

### Instance Properties

The following properties are available on instances of `Session`:

#### `ses.cookies`

Returns an instance of `Cookies` class for this session.

#### `ses.webRequest`

Returns an instance of `WebRequest` class for this session.

#### `ses.protocol`

Returns an instance of [protocol](protocol.md) module for this session.

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

app.on('ready', function () {
  const protocol = session.fromPartition(partitionName).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')
  })
})
```

## Class: Cookies

The `Cookies` class gives you ability to query and modify cookies. Instances of
`Cookies` class must be received by using `cookies` property of `Session` class.

For example:

```javascript
// Query all cookies.
session.defaultSession.cookies.get({}, (error, cookies) => {
  console.log(cookies)
})

// Query all cookies associated with a specific url.
session.defaultSession.cookies.get({url: 'http://www.github.com'}, (error, cookies) => {
  console.log(cookies)
})

// Set a cookie with the given cookie data;
// may overwrite equivalent cookies if they exist.
const cookie = {url: 'http://www.github.com', name: 'dummy_name', value: 'dummy'}
session.defaultSession.cookies.set(cookie, (error) => {
  if (error)
    console.error(error)
})
```

### Instance Methods

The following methods are available on instances of `Cookies`:

#### `cookies.get(filter, callback)`

* `filter` Object
  * `url` String (optional) - Retrieves cookies which are associated with
    `url`. Empty implies retrieving cookies of all urls.
  * `name` String (optional) - Filters cookies by name.
  * `domain` String (optional) - Retrieves cookies whose domains match or are
    subdomains of `domains`
  * `path` String (optional) - Retrieves cookies whose path matches `path`.
  * `secure` Boolean (optional) - Filters cookies by their Secure property.
  * `session` Boolean (optional) - Filters out session or persistent cookies.
* `callback` Function

Sends a request to get all cookies matching `details`, `callback` will be called
with `callback(error, cookies)` on complete.

`cookies` is an Array of `cookie` objects.

* `cookie` Object
  *  `name` String - The name of the cookie.
  *  `value` String - The value of the cookie.
  *  `domain` String - The domain of the cookie.
  *  `hostOnly` String - Whether the cookie is a host-only cookie.
  *  `path` String - The path of the cookie.
  *  `secure` Boolean - Whether the cookie is marked as secure.
  *  `httpOnly` Boolean - Whether the cookie is marked as HTTP only.
  *  `session` Boolean - Whether the cookie is a session cookie or a persistent
     cookie with an expiration date.
  *  `expirationDate` Double (optional) - The expiration date of the cookie as
     the number of seconds since the UNIX epoch. Not provided for session
     cookies.

#### `cookies.set(details, callback)`

* `details` Object
  * `url` String - The url to associate the cookie with.
  * `name` String - The name of the cookie. Empty by default if omitted.
  * `value` String - The value of the cookie. Empty by default if omitted.
  * `domain` String - The domain of the cookie. Empty by default if omitted.
  * `path` String - The path of the cookie. Empty by default if omitted.
  * `secure` Boolean - Whether the cookie should be marked as Secure. Defaults to
    false.
  * `httpOnly` Boolean - Whether the cookie should be marked as HTTP only.
    Defaults to false.
  * `expirationDate` Double -	The expiration date of the cookie as the number of
    seconds since the UNIX epoch. If omitted then the cookie becomes a session
    cookie and will not be retained between sessions.
* `callback` Function

Sets a cookie with `details`, `callback` will be called with `callback(error)`
on complete.

#### `cookies.remove(url, name, callback)`

* `url` String - The URL associated with the cookie.
* `name` String - The name of cookie to remove.
* `callback` Function

Removes the cookies matching `url` and `name`, `callback` will called with
`callback()` on complete.

## Class: WebRequest

The `WebRequest` class allows to intercept and modify contents of a request at
various stages of its lifetime. Instances of `WebRequest` class must be received
by using `webRequest` property of `Session` class.

The methods of `WebRequest` accept an optional `filter` and a `listener`, the
`listener` will be called with `listener(details)` when the API's event has
happened, the `details` is an object that describes the request. Passing `null`
as `listener` will unsubscribe from the event.

The `filter` is an object that has an `urls` property, which is an Array of URL
patterns that will be used to filter out the requests that do not match the URL
patterns. If the `filter` is omitted then all requests will be matched.

For certain events the `listener` is passed with a `callback`, which should be
called with an `response` object when `listener` has done its work.

An example of adding `User-Agent` header for requests:

```javascript
// Modify the user agent for all requests to the following urls.
const filter = {
  urls: ['https://*.github.com/*', '*://electron.github.io']
}

session.defaultSession.webRequest.onBeforeSendHeaders(filter, (details, callback) => {
  details.requestHeaders['User-Agent'] = "MyAgent"
  callback({cancel: false, requestHeaders: details.requestHeaders})
})
```

### Instance Methods

The following methods are available on instances of `WebRequest`:

#### `webRequest.onBeforeRequest([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details, callback)` when a request
is about to occur.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `uploadData` Array (optional)
* `callback` Function

The `uploadData` is an array of `data` objects:

* `data` Object
  * `bytes` Buffer - Content being sent.
  * `file` String - Path of file being uploaded.

The `callback` has to be called with an `response` object:

* `response` Object
  * `cancel` Boolean (optional)
  * `redirectURL` String (optional) - The original request is prevented from
    being sent or completed, and is instead redirected to the given URL.

#### `webRequest.onBeforeSendHeaders([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details, callback)` before sending
an HTTP request, once the request headers are available. This may occur after a
TCP connection is made to the server, but before any http data is sent.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `requestHeaders` Object
* `callback` Function

The `callback` has to be called with an `response` object:

* `response` Object
  * `cancel` Boolean (optional)
  * `requestHeaders` Object (optional) - When provided, request will be made
    with these headers.

#### `webRequest.onSendHeaders([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details)` just before a request is
going to be sent to the server, modifications of previous `onBeforeSendHeaders`
response are visible by the time this listener is fired.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `requestHeaders` Object

#### `webRequest.onHeadersReceived([filter,]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details, callback)` when HTTP
response headers of a request have been received.

* `details` Object
  * `id` String
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `statusLine` String
  * `statusCode` Integer
  * `responseHeaders` Object
* `callback` Function

The `callback` has to be called with an `response` object:

* `response` Object
  * `cancel` Boolean
  * `responseHeaders` Object (optional) - When provided, the server is assumed
    to have responded with these headers.
  * `statusLine` String (optional) - Should be provided when overriding
    `responseHeaders` to change header status otherwise original response
    header's status will be used.

#### `webRequest.onResponseStarted([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details)` when first byte of the
response body is received. For HTTP requests, this means that the status line
and response headers are available.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `responseHeaders` Object
  * `fromCache` Boolean - Indicates whether the response was fetched from disk
    cache.
  * `statusCode` Integer
  * `statusLine` String

#### `webRequest.onBeforeRedirect([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details)` when a server initiated
redirect is about to occur.

* `details` Object
  * `id` String
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `redirectURL` String
  * `statusCode` Integer
  * `ip` String (optional) - The server IP address that the request was
    actually sent to.
  * `fromCache` Boolean
  * `responseHeaders` Object

#### `webRequest.onCompleted([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details)` when a request is
completed.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `responseHeaders` Object
  * `fromCache` Boolean
  * `statusCode` Integer
  * `statusLine` String

#### `webRequest.onErrorOccurred([filter, ]listener)`

* `filter` Object
* `listener` Function

The `listener` will be called with `listener(details)` when an error occurs.

* `details` Object
  * `id` Integer
  * `url` String
  * `method` String
  * `resourceType` String
  * `timestamp` Double
  * `fromCache` Boolean
  * `error` String - The error description.