Class: WebRequest

Intercept and modify the contents of a request at various stages of its lifetime.

Process: Main

Instances of the WebRequest class are accessed by using the webRequest property of a Session.

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 object describes the request.

⚠️ Only the last attached listener will be used. Passing null as listener will unsubscribe from the event.

The filter object has a 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 a response object when listener has done its work.

An example of adding User-Agent header for requests:

const { session } = require('electron')

// 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({ requestHeaders: details.requestHeaders })
})

Instance Methods

The following methods are available on instances of WebRequest:

webRequest.onBeforeRequest([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • uploadData UploadData[]
  • callback Function
    • 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.

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

The uploadData is an array of UploadData objects.

The callback has to be called with an response object.

Some examples of valid urls:

'http://foo:1234/'
'http://foo.com/'
'http://foo:1234/bar'
'*://*/*'
'*://example.com/*'
'*://example.com/foo/*'
'http://*.foo:1234/'
'file://foo:1234/bar'
'http://foo:*/'
'*://www.foo.com/'

webRequest.onBeforeSendHeaders([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • requestHeaders Record<string, string>
  • callback Function
    • beforeSendResponse Object cancel Boolean (optional) requestHeaders Record<string, string | string[]> (optional) - When provided, request will be made with these headers.

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.

The callback has to be called with a response object.

webRequest.onSendHeaders([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • requestHeaders Record<string, string>

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.

webRequest.onHeadersReceived([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • statusLine String
    • statusCode Integer
    • requestHeaders Record<string, string>
    • responseHeaders Record<string, string[]> (optional)
  • callback Function
    • headersReceivedResponse Object
      • cancel Boolean (optional)
      • responseHeaders Record<string, string | string[]> (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.

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

The callback has to be called with a response object.

webRequest.onResponseStarted([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • responseHeaders Record<string, string[]> (optional)
    • fromCache Boolean - Indicates whether the response was fetched from disk cache.
    • statusCode Integer
    • statusLine String

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.

webRequest.onBeforeRedirect([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • redirectURL String
    • statusCode Integer
    • statusLine String
    • ip String (optional) - The server IP address that the request was actually sent to.
    • fromCache Boolean
    • responseHeaders Record<string, string[]> (optional)

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

webRequest.onCompleted([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • responseHeaders Record<string, string[]> (optional)
    • fromCache Boolean
    • statusCode Integer
    • statusLine String
    • error String

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

webRequest.onErrorOccurred([filter, ]listener)

• filter Object (optional)
  • urls String[] - Array of URL patterns that will be used to filter out the requests that do not match the URL patterns.
• listener Function | null
  • details Object
    • id Integer
    • url String
    • method String
    • webContentsId Integer (optional)
    • resourceType String
    • referrer String
    • timestamp Double
    • fromCache Boolean
    • error String - The error description.

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