The Qt WebEngine module provides a web browser engine that makes it easy to embed content from the World Wide Web into your Qt application on platforms that do not have a native web engine.

Qt WebEngine provides C++ classes and QML types for rendering HTML, XHTML, and SVG documents, styled using Cascading Style Sheets (CSS) and scripted with JavaScript. HTML documents can be made fully editable by the user through the use of thecontenteditable attribute on HTML elements.

Qt WebEngine Architecture

The functionality in Qt WebEngine is divided into the following modules:

• Qt WebEngine Widgets Module for creating widget-based web applications
• Qt WebEngine Module for creating Qt Quick based web applications
• Qt WebEngine Core Module for interacting with Chromium

Page rendering and JavaScript execution are separated from the GUI process into the Qt WebEngine Process. It is a library that must be shipped with the application if the Qt libraries are bundled into the application.

Qt WebEngine Widgets Module

Aweb engine view is the main widget component of the Qt WebEngine module. It can be used in various applications to load web content. Within a view, aweb engine page holds a main frame that is responsible for web content, thehistory of navigated links, andactions. The view and page are quite similar, as they provide a set of common functions.

All pages belong to aweb engine profile that contains sharedsettings,scripts, andcookies. Profiles can be used to isolate pages from each other. A typical use case is a dedicated profile for aprivate browsing mode, where no information is permanently saved.

Qt WebEngine Module

The Qt WebEngine QML implementation contains the same elements as the Qt WebEngine Widgets implementation, except that there is no separately accessible web engine page. The supported page functionality is integrated into the web engine view.

Qt WebEngine Core Module

The Qt WebEngine core is based on theChromium Project. Chromium provides its own network and painting engines and is developed tightly together with its dependent modules.

This version of Qt WebEngine is based on Chromium version 87.0.4280, with additional security fixes from newer versions.

Qt WebEngine Process

The Qt WebEngine Process is a separate executable that is used to render web pages and execute JavaScript. This mitigates security issues and isolates crashes caused by specific content.

Embedding Web Content into Widget Based Applications

Use theQWebEngineView class to display web pages in the simplest way. Because it is a widget, you can embedQWebEngineView into your forms and use its convenience functions to download and display web sites.

QWebEngineView*view=newQWebEngineView(parent);view->load(QUrl("http://www.qt.io/"));view->show();

An instance ofQWebEngineView has oneQWebEnginePage.QWebEnginePage can have aQWebEngineHistory that provides access to the page's navigation history and severalQAction objects that apply actions on the web page. In addition, aQWebEnginePage has the ability to run JavaScript code in the context of the page's main frame and to enable customization of handlers for specific events like showing custom authentication dialogs.

EachQWebEnginePage belongs to aQWebEngineProfile that can have aQWebEngineSettings for specifying page settings, aQWebEngineScriptCollection for running scripts on the page, and aQWebEngineCookieStore for accessing the HTTP cookies of Chromium. AQWebEnginePage can also directly point to a script collection.

For a widget based application, the web engine is automatically initialized, unless it is placed in a plugin. In that case, it must be initialized in the application main source file by usingQtWebEngine::initialize, as illustrated by the following code snippet:

int main(int argc,char**argv){QApplication app(argc, argv);QtWebEngine::initialize();QMainWindow window;    window.show();return app.exec();}

Embedding Web Content into Qt Quick Applications

TheWebEngineView QML type allows Qt Quick applications to render regions of dynamic web content. AWebEngineView type may share the screen with other QML types or encompass the full screen as specified within the Qt Quick application.

To make sure that OpenGL context can be shared between the GUI and render processes, the web engine must be initialized by usingQtWebEngine::initialize in the application main source file, as illustrated by the following code snippet:

int main(int argc,char*argv[]){QGuiApplication app(argc, argv);QtWebEngine::initialize();QQmlApplicationEngine engine;    engine.load(QUrl("qrc:/main.qml"));return app.exec();}

An application can load pages into theWebEngineView, using either an URL or HTML string, and navigate within session history. By default, links to different pages load within the sameWebEngineView object, but web sites may request them to be opened as a new tab, window, or dialog.

The following sample QML application loads a web page using theurl property:

import QtQuick 2.0import QtQuick.Window 2.0import QtWebEngine 1.0Window {width:1024height:750visible:trueWebEngineView {anchors.fill:parenturl:"https://www.qt.io"    }}

Script Injection

Qt WebEngine does not allow direct access to the document object model (DOM) of a page. However, the DOM can be inspected and adapted by injecting scripts.

The DOM of a page is constructed when the document is ready, typically when the page is completely loaded. Therefore, executing scripts as soon as a document is created is not suitable for DOM operations, where one has to wait until the DOM is ready.

In addition, an injected script shares the sameworld as the other scripts executed on the page, which might lead to conflicts. To avoid this, theQWebEngineScript class and theWebEngineScript QML type provide implementations of the Chromium API forContent Script Extensions. They specify the script to run, the injection point, and the world where the script is run. This enables accessing the DOM to manipulate it within a world.

Since Qt 5.8, Qt WebEngine supports augmenting a script by using the followingGreasemonkey-like attributes:

• @exclude <regexp>
• @include <regexp>
• @match <regexp>
• @name <free text>
• @run-at [document-start|document-end|document-idle]

The attributes determine if and when auser script is run. They must be placed immediately in the beginning of the script, inside a==UserScript== comment:

// ==UserScript==// @include http://*.qt.io/*// @exclude http://wiki.qt.io/*// ==/UserScript==window.alert("Page is from qt.io, but not wiki.qt.io");

If yourWebEngine application is built using the Qt Quick Compiler, and the application ships JavaScript files inside .qrc resources, consider reading the sectionJavaScript Files in Qt Resource Files.

Managing Certificates

Qt WebEngine uses its own network stack, and thereforeQSslConfiguration is not used to open SSL connections. Instead, Qt WebEngine uses the root CA certificates from the operating system to validate the peer's certificate.

TheWebEngineCertificateError::error andQWebEngineCertificateError::Error enumerations provide information about the types of certificate errors that might occur. The errors can be handled by using theWebEngineView::certificateError QML method or by reimplementing theQWebEnginePage::certificateError function.

Proxy Support

Qt WebEngine uses the proxy settings fromQt Network, and forwards them to Chromium's networking stack. IfQNetworkProxy::applicationProxy is set, it will also be used for Qt WebEngine. IfQNetworkProxyFactory::usesSystemConfiguration() is enabled, the proxy settings are automatically retrieved from the system. Settings from an installedQNetworkProxyFactory will be ignored, though.

In caseQNetworkProxy::user() andQNetworkProxy::password() are set, these credentials will be automatically used for proxy authentication. It is up to the user to provide valid credentials, since there is no error handling callback.

If no credentials are set withQNetworkProxy, but the proxy requires authentication,QWebEnginePage::proxyAuthenticationRequired is emitted. For Qt Quick, a dialog is shown.

Not all properties ofQNetworkProxy are supported by Qt WebEngine. That is,QNetworkProxy::type(),QNetworkProxy::hostName() andQNetworkProxy::port() are taken into account. All other proxy settings such asQNetworkProxy::rawHeader() are ignored.

High DPI Support

To support High DPI devices, it is recommended that the application attributeQt::AA_EnableHighDpiScaling is set to enable automatic scaling based on the pixel density of the monitor. In Qt WebEngine applications, the scaling affects the default zooming factor and scrollbar size.

For example:

int main(int argc,char*argv[]){QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);QApplication app(argc, argv);// ...}

Qt WebEngine bundles images for normal and high-dpi resolutions intoqtwebengine_resources_100p.pak andqtwebengine_resources_200p.pak files. Depending on the target resolutions, one or both of these files need to be deployed.

For more information, seeHigh DPI Displays.

Using WebEngine Core

Qt WebEngine Core provides an API shared by Qt WebEngine and Qt WebEngine Widgets for handling URL requests issued for the networking stack of Chromium and for accessing its HTTP cookies.

Implementing theQWebEngineUrlRequestInterceptor interface and installing the interceptor on a profile enables intercepting, blocking, and modifying URL requests (QWebEngineUrlRequestInfo) before they reach the networking stack of Chromium.

AQWebEngineUrlSchemeHandler can be registered for a profile to add support for custom URL schemes. Requests for the scheme are then issued toQWebEngineUrlSchemeHandler::requestStarted() asQWebEngineUrlRequestJob objects.

TheQWebEngineCookieStore class provides functions for accessing HTTP cookies of Chromium. The functions can be used to synchronize cookies withQNetworkAccessManager, as well as to set, delete, and intercept cookies during navigation.

Platform Notes

Qt WebEngine currently supports only Windows, Linux, and macOS. Due to Chromium build requirements it also often requires a newer compiler than the rest of Qt. SeeQt WebEngine Platform Notes for further details.

Related Modules

Qt WebEngine supersedes theQt WebKit module, which is based on theWebKit project, but has not been actively synchronized with the upstreamWebKit code since Qt 5.2 and has been deprecated in Qt 5.5. For tips on how to change a Qt WebKit widgets application to use Qt WebEngine widgets, seePorting from Qt WebKit to Qt WebEngine.

TheQt WebView module allows to use a native web browser on platforms where one is available.

TheQt WebChannel module can be used to create a bi-directional communication channel betweenQObject objects on the C++ side and JavaScript on the QML side.