webContents

webContents is an EventEmitter.

It is responsible for rendering and controlling a web page and is a property of the BrowserWindow object. An example of accessing the webContents object:

const BrowserWindow = require('electron').BrowserWindow;

var win = new BrowserWindow({width: 800, height: 1500});
win.loadURL("http://github.com");

var webContents = win.webContents;

Events

The webContents object emits the following events:

Event: 'did-finish-load'

Emitted when the navigation is done, i.e. the spinner of the tab has stopped spinning, and the onload event was dispatched.

Event: 'did-fail-load'

Returns:

• event Event
• errorCode Integer
• errorDescription String
• validatedURL String

This event is like did-finish-load but emitted when the load failed or was cancelled, e.g. window.stop() is invoked. The full list of error codes and their meaning is available here.

Event: 'did-frame-finish-load'

Returns:

• event Event
• isMainFrame Boolean

Emitted when a frame has done navigation.

Event: 'did-start-loading'

Corresponds to the points in time when the spinner of the tab started spinning.

Event: 'did-stop-loading'

Corresponds to the points in time when the spinner of the tab stopped spinning.

Event: 'did-get-response-details'

Returns:

• event Event
• status Boolean
• newURL String
• originalURL String
• httpResponseCode Integer
• requestMethod String
• referrer String
• headers Object

Emitted when details regarding a requested resource are available. status indicates the socket connection to download the resource.

Event: 'did-get-redirect-request'

Returns:

• event Event
• oldURL String
• newURL String
• isMainFrame Boolean
• httpResponseCode Integer
• requestMethod String
• referrer String
• headers Object

Emitted when a redirect is received while requesting a resource.

Event: 'dom-ready'

Returns:

• event Event

Emitted when the document in the given frame is loaded.

Event: 'page-favicon-updated'

Returns:

• event Event
• favicons Array - Array of URLs

Emitted when page receives favicon urls.

Event: 'new-window'

Returns:

• event Event
• url String
• frameName String
• disposition String - Can be default, foreground-tab, background-tab, new-window and other.
• options Object - The options which will be used for creating the new BrowserWindow.

Emitted when the page requests to open a new window for a url. It could be requested by window.open or an external link like <a target='_blank'>.

By default a new BrowserWindow will be created for the url.

Calling event.preventDefault() will prevent creating new windows.

Event: 'will-navigate'

Returns:

• event Event
• url String

Emitted when a user or the page wants to start navigation. It can happen when the window.location object is changed or a user clicks a link in the page.

This event will not emit when the navigation is started programmatically with APIs like webContents.loadURL and webContents.back.

It is also not emitted for in-page navigations, such as clicking anchor links or updating the window.location.hash. Use did-navigate-in-page event for this purpose.

Calling event.preventDefault() will prevent the navigation.

Event: 'did-navigate'

Returns:

• event Event
• url String

Emitted when a navigation is done.

This event is not emitted for in-page navigations, such as clicking anchor links or updating the window.location.hash. Use did-navigate-in-page event for this purpose.

Event: 'did-navigate-in-page'

Returns:

• event Event
• url String

Emitted when an in-page navigation happened.

When in-page navigation happens, the page URL changes but does not cause navigation outside of the page. Examples of this occurring are when anchor links are clicked or when the DOM hashchange event is triggered.

Event: 'crashed'

Emitted when the renderer process has crashed.

Event: 'plugin-crashed'

Returns:

• event Event
• name String
• version String

Emitted when a plugin process has crashed.

Event: 'destroyed'

Emitted when webContents is destroyed.

Event: 'devtools-opened'

Emitted when DevTools is opened.

Event: 'devtools-closed'

Emitted when DevTools is closed.

Event: 'devtools-focused'

Emitted when DevTools is focused / opened.

Event: 'certificate-error'

Returns:

• event Event
• url URL
• error String - The error code
• certificate Object
  • data Buffer - PEM encoded data
  • issuerName String
• callback Function

Emitted when failed to verify the certificate for url.

The usage is the same with the certificate-error event of app.

Event: 'select-client-certificate'

Returns:

• event Event
• url URL
• certificateList [Objects]
  • data Buffer - PEM encoded data
  • issuerName String - Issuer's Common Name
• callback Function

Emitted when a client certificate is requested.

The usage is the same with the select-client-certificate event of app.

Event: 'login'

Returns:

• event Event
• request Object
  • method String
  • url URL
  • referrer URL
• authInfo Object
  • isProxy Boolean
  • scheme String
  • host String
  • port Integer
  • realm String
• callback Function

Emitted when webContents wants to do basic auth.

The usage is the same with the login event of app.

Event: 'found-in-page'

Returns:

• event Event
• result Object
  • requestId Integer
  • finalUpdate Boolean - Indicates if more responses are to follow.
  • matches Integer (optional) - Number of Matches.
  • selectionArea Object (optional) - Coordinates of first match region.

Emitted when a result is available for webContents.findInPage request.

Event: 'media-started-playing'

Emitted when media starts playing.

Event: 'media-paused'

Emitted when media is paused or done playing.

Event: 'did-change-theme-color'

Emitted when a page's theme color changes. This is usually due to encountering a meta tag:

<meta name='theme-color' content='#ff0000'>

Event: 'cursor-changed'

Returns:

• event Event
• type String
• image NativeImage (optional)
• scale Float (optional)

Emitted when the cursor's type changes. The type parameter can be default, crosshair, pointer, text, wait, help, e-resize, n-resize, ne-resize, nw-resize, s-resize, se-resize, sw-resize, w-resize, ns-resize, ew-resize, nesw-resize, nwse-resize, col-resize, row-resize, m-panning, e-panning, n-panning, ne-panning, nw-panning, s-panning, se-panning, sw-panning, w-panning, move, vertical-text, cell, context-menu, alias, progress, nodrop, copy, none, not-allowed, zoom-in, zoom-out, grab, grabbing, custom.

If the type parameter is custom, the image parameter will hold the custom cursor image in a NativeImage, and the scale will hold scaling information for the image.

Instance Methods

The webContents object has the following instance methods:

webContents.loadURL(url[, options])

• url URL
• options Object (optional)
  • httpReferrer String - A HTTP Referrer url.
  • userAgent String - A user agent originating the request.
  • extraHeaders String - Extra headers separated by "\n"

Loads the url in the window, the url must contain the protocol prefix, e.g. the http:// or file://. If the load should bypass http cache then use the pragma header to achieve it.

const options = {"extraHeaders" : "pragma: no-cache\n"}
webContents.loadURL(url, options)

webContents.downloadURL(url)

• url URL

Initiates a download of the resource at url without navigating. The will-download event of session will be triggered.

webContents.getURL()

Returns URL of the current web page.

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

var currentURL = win.webContents.getURL();

webContents.getTitle()

Returns the title of the current web page.

webContents.isLoading()

Returns whether web page is still loading resources.

webContents.isWaitingForResponse()

Returns whether the web page is waiting for a first-response from the main resource of the page.

webContents.stop()

Stops any pending navigation.

webContents.reload()

Reloads the current web page.

webContents.reloadIgnoringCache()

Reloads current page and ignores cache.

webContents.canGoBack()

Returns whether the browser can go back to previous web page.

webContents.canGoForward()

Returns whether the browser can go forward to next web page.

webContents.canGoToOffset(offset)

• offset Integer

Returns whether the web page can go to offset.

webContents.clearHistory()

Clears the navigation history.

webContents.goBack()

Makes the browser go back a web page.

webContents.goForward()

Makes the browser go forward a web page.

webContents.goToIndex(index)

• index Integer

Navigates browser to the specified absolute web page index.

webContents.goToOffset(offset)

• offset Integer

Navigates to the specified offset from the "current entry".

webContents.isCrashed()

Whether the renderer process has crashed.

webContents.setUserAgent(userAgent)

• userAgent String

Overrides the user agent for this web page.

webContents.getUserAgent()

Returns a String representing the user agent for this web page.

webContents.insertCSS(css)

• css String

Injects CSS into the current web page.

webContents.executeJavaScript(code[, userGesture, callback])

• code String
• userGesture Boolean (optional)
• callback Function (optional) - Called after script has been executed.
  • result

Evaluates code in page.

In the browser window some HTML APIs like requestFullScreen can only be invoked by a gesture from the user. Setting userGesture to true will remove this limitation.

webContents.setAudioMuted(muted)

• muted Boolean

Mute the audio on the current web page.

webContents.isAudioMuted()

Returns whether this page has been muted.

webContents.undo()

Executes the editing command undo in web page.

webContents.redo()

Executes the editing command redo in web page.

webContents.cut()

Executes the editing command cut in web page.

webContents.copy()

Executes the editing command copy in web page.

webContents.paste()

Executes the editing command paste in web page.

webContents.pasteAndMatchStyle()

Executes the editing command pasteAndMatchStyle in web page.

webContents.delete()

Executes the editing command delete in web page.

webContents.selectAll()

Executes the editing command selectAll in web page.

webContents.unselect()

Executes the editing command unselect in web page.

webContents.replace(text)

• text String

Executes the editing command replace in web page.

webContents.replaceMisspelling(text)

• text String

Executes the editing command replaceMisspelling in web page.

webContents.insertText(text)

• text String

Inserts text to the focused element.

webContents.findInPage(text[, options])

• text String - Content to be searched, must not be empty.
• options Object (optional)
  • forward Boolean - Whether to search forward or backward, defaults to true.
  • findNext Boolean - Whether the operation is first request or a follow up, defaults to false.
  • matchCase Boolean - Whether search should be case-sensitive, defaults to false.
  • wordStart Boolean - Whether to look only at the start of words. defaults to false.
  • medialCapitalAsWordStart Boolean - When combined with wordStart, accepts a match in the middle of a word if the match begins with an uppercase letter followed by a lowercase or non-letter. Accepts several other intra-word matches, defaults to false.

Starts a request to find all matches for the text in the web page and returns an Integer representing the request id used for the request. The result of the request can be obtained by subscribing to found-in-page event.

webContents.stopFindInPage(action)

• action String - Specifies the action to take place when ending webContents.findInPage request.
  • clearSelection - Translate the selection into a normal selection.
  • keepSelection - Clear the selection.
  • activateSelection - Focus and click the selection node.

Stops any findInPage request for the webContents with the provided action.

webContents.on('found-in-page', function(event, result) {
  if (result.finalUpdate)
    webContents.stopFindInPage("clearSelection");
});

const requestId = webContents.findInPage("api");

webContents.hasServiceWorker(callback)

• callback Function

Checks if any ServiceWorker is registered and returns a boolean as response to callback.

webContents.unregisterServiceWorker(callback)

• callback Function

Unregisters any ServiceWorker if present and returns a boolean as response to callback when the JS promise is fulfilled or false when the JS promise is rejected.

webContents.print([options])

• options Object (optional)
  • silent Boolean - Don't ask user for print settings. Default is false.
  • printBackground Boolean - Also prints the background color and image of the web page. Default is false.

Prints window's web page. When silent is set to false, Electron will pick up system's default printer and default settings for printing.

Calling window.print() in web page is equivalent to calling webContents.print({silent: false, printBackground: false}).

Note: On Windows, the print API relies on pdf.dll. If your application doesn't need the print feature, you can safely remove pdf.dll to reduce binary size.

webContents.printToPDF(options, callback)

• options Object
  • marginsType Integer - Specifies the type of margins to use. Uses 0 for default margin, 1 for no margin, and 2 for minimum margin.
  • pageSize String - Specify page size of the generated PDF. Can be A3, A4, A5, Legal, Letter and Tabloid.
  • printBackground Boolean - Whether to print CSS backgrounds.
  • printSelectionOnly Boolean - Whether to print selection only.
  • landscape Boolean - true for landscape, false for portrait.
• callback Function

Prints window's web page as PDF with Chromium's preview printing custom settings.

The callback will be called with callback(error, data) on completion. The data is a Buffer that contains the generated PDF data.

By default, an empty options will be regarded as:

{
  marginsType: 0,
  printBackground: false,
  printSelectionOnly: false,
  landscape: false
}

const BrowserWindow = require('electron').BrowserWindow;
const fs = require('fs');

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

win.webContents.on("did-finish-load", function() {
  // Use default printing options
  win.webContents.printToPDF({}, function(error, data) {
    if (error) throw error;
    fs.writeFile("/tmp/print.pdf", data, function(error) {
      if (error)
        throw error;
      console.log("Write PDF successfully.");
    })
  })
});

webContents.addWorkSpace(path)

• path String

Adds the specified path to DevTools workspace. Must be used after DevTools creation:

mainWindow.webContents.on('devtools-opened', function() {
  mainWindow.webContents.addWorkSpace(__dirname);
});

webContents.removeWorkSpace(path)

• path String

Removes the specified path from DevTools workspace.

webContents.openDevTools([options])

• options Object (optional)
  • detach Boolean - opens DevTools in a new window

Opens the devtools.

webContents.closeDevTools()

Closes the devtools.

webContents.isDevToolsOpened()

Returns whether the devtools is opened.

webContents.isDevToolsFocused()

Returns whether the devtools view is focused .

webContents.toggleDevTools()

Toggles the developer tools.

webContents.inspectElement(x, y)

• x Integer
• y Integer

Starts inspecting element at position (x, y).

webContents.inspectServiceWorker()

Opens the developer tools for the service worker context.

webContents.send(channel[, arg1][, arg2][, ...])

• channel String
• arg (optional)

Send an asynchronous message to renderer process via channel, you can also send arbitrary arguments. Arguments will be serialized in JSON internally and hence no functions or prototype chain will be included.

The renderer process can handle the message by listening to channel with the ipcRenderer module.

An example of sending messages from the main process to the renderer process:

// In the main process.
var window = null;
app.on('ready', function() {
  window = new BrowserWindow({width: 800, height: 600});
  window.loadURL('file://' + __dirname + '/index.html');
  window.webContents.on('did-finish-load', function() {
    window.webContents.send('ping', 'whoooooooh!');
  });
});

<!-- index.html -->
<html>
<body>
  <script>
    require('electron').ipcRenderer.on('ping', function(event, message) {
      console.log(message);  // Prints "whoooooooh!"
    });
  </script>
</body>
</html>

webContents.enableDeviceEmulation(parameters)

parameters Object, properties:

• screenPosition String - Specify the screen type to emulate (default: desktop)
  • desktop
  • mobile
• screenSize Object - Set the emulated screen size (screenPosition == mobile)
  • width Integer - Set the emulated screen width
  • height Integer - Set the emulated screen height
• viewPosition Object - Position the view on the screen (screenPosition == mobile) (default: {x: 0, y: 0})
  • x Integer - Set the x axis offset from top left corner
  • y Integer - Set the y axis offset from top left corner
• deviceScaleFactor Integer - Set the device scale factor (if zero defaults to original device scale factor) (default: 0)
• viewSize Object - Set the emulated view size (empty means no override)
  • width Integer - Set the emulated view width
  • height Integer - Set the emulated view height
• fitToView Boolean - Whether emulated view should be scaled down if necessary to fit into available space (default: false)
• offset Object - Offset of the emulated view inside available space (not in fit to view mode) (default: {x: 0, y: 0})
  • x Float - Set the x axis offset from top left corner
  • y Float - Set the y axis offset from top left corner
• scale Float - Scale of emulated view inside available space (not in fit to view mode) (default: 1)

Enable device emulation with the given parameters.

webContents.disableDeviceEmulation()

Disable device emulation enabled by webContents.enableDeviceEmulation.

webContents.sendInputEvent(event)

• event Object
  • type String (required) - The type of the event, can be mouseDown, mouseUp, mouseEnter, mouseLeave, contextMenu, mouseWheel, mouseMove, keyDown, keyUp, char.
  • modifiers Array - An array of modifiers of the event, can include shift, control, alt, meta, isKeypad, isAutoRepeat, leftButtonDown, middleButtonDown, rightButtonDown, capsLock, numLock, left, right.

Sends an input event to the page.

For keyboard events, the event object also have following properties:

• keyCode Char or String (required) - The character that will be sent as the keyboard event. Can be a single UTF-8 character, or the name of the key that generates the event. Accepted key names are enter, backspace, delete, tab, escape, control, alt, altgr (Windows only), shift, end, home, insert, left, up, right, down, pageUp, pageDown, printScreen, meta, cmd (OSX only), command (OSX only), option (OSX only)

For mouse events, the event object also have following properties:

• x Integer (required)
• y Integer (required)
• button String - The button pressed, can be left, middle, right
• globalX Integer
• globalY Integer
• movementX Integer
• movementY Integer
• clickCount Integer

For the mouseWheel event, the event object also have following properties:

• deltaX Integer
• deltaY Integer
• wheelTicksX Integer
• wheelTicksY Integer
• accelerationRatioX Integer
• accelerationRatioY Integer
• hasPreciseScrollingDeltas Boolean
• canScroll Boolean

webContents.beginFrameSubscription(callback)

• callback Function

Begin subscribing for presentation events and captured frames, the callback will be called with callback(frameBuffer) when there is a presentation event.

The frameBuffer is a Buffer that contains raw pixel data. On most machines, the pixel data is effectively stored in 32bit BGRA format, but the actual representation depends on the endianness of the processor (most modern processors are little-endian, on machines with big-endian processors the data is in 32bit ARGB format).

webContents.endFrameSubscription()

End subscribing for frame presentation events.

webContents.savePage(fullPath, saveType, callback)

• fullPath String - The full file path.
• saveType String - Specify the save type.
  • HTMLOnly - Save only the HTML of the page.
  • HTMLComplete - Save complete-html page.
  • MHTML - Save complete-html page as MHTML.
• callback Function - function(error) {}.
  • error Error

Returns true if the process of saving page has been initiated successfully.

win.loadURL('https://github.com');

win.webContents.on('did-finish-load', function() {
  win.webContents.savePage('/tmp/test.html', 'HTMLComplete', function(error) {
    if (!error)
      console.log("Save page successfully");
  });
});

Instance Properties

WebContents objects also have the following properties:

webContents.session

Returns the session object used by this webContents.

webContents.hostWebContents

Returns the WebContents that might own this WebContents.

webContents.devToolsWebContents

Get the WebContents of DevTools for this WebContents.

Note: Users should never store this object because it may become null when the DevTools has been closed.

webContents.debugger

Debugger API serves as an alternate transport for remote debugging protocol.

try {
  win.webContents.debugger.attach("1.1");
} catch(err) {
  console.log("Debugger attach failed : ", err);
};

win.webContents.debugger.on('detach', function(event, reason) {
  console.log("Debugger detached due to : ", reason);
});

win.webContents.debugger.on('message', function(event, method, params) {
  if (method == "Network.requestWillBeSent") {
    if (params.request.url == "https://www.github.com")
      win.webContents.debugger.detach();
  }
})

win.webContents.debugger.sendCommand("Network.enable");

webContents.debugger.attach([protocolVersion])

• protocolVersion String (optional) - Requested debugging protocol version.

Attaches the debugger to the webContents.

webContents.debugger.isAttached()

Returns a boolean indicating whether a debugger is attached to the webContents.

webContents.debugger.detach()

Detaches the debugger from the webContents.

webContents.debugger.sendCommand(method[, commandParams, callback])

• method String - Method name, should be one of the methods defined by the remote debugging protocol.
• commandParams Object (optional) - JSON object with request parameters.
• callback Function (optional) - Response
  • error Object - Error message indicating the failure of the command.
  • result Object - Response defined by the 'returns' attribute of the command description in the remote debugging protocol.

Send given command to the debugging target.

Event: 'detach'

• event Event
• reason String - Reason for detaching debugger.

Emitted when debugging session is terminated. This happens either when webContents is closed or devtools is invoked for the attached webContents.

Event: 'message'

• event Event
• method String - Method name.
• params Object - Event parameters defined by the 'parameters' attribute in the remote debugging protocol.

Emitted whenever debugging target issues instrumentation event.