Web engine

The following renderers are used on each platform

Platform Code Renderer Provider Browser compatibility
GTK gtk WebKit WebKit2
macOS WebKit WebKit.WKWebView (bundled with OS)
QT qt WebKit QtWebEngine / QtWebKit
Windows edgechromium Chromium > .NET Framework 4.6.2 and Edge Runtime installed Ever-green Chromium
Windows edgehtml EdgeHTML > .NET Framework 4.6.2 and Windows 10 build 17110
Windows mshtml MSHTML MSHTML via .NET / System.Windows.Forms.WebBrowser IE11 (Windows 10/8/7)
Windows cef CEF CEF Python Chrome 66

On Windows renderer is chosen in the following order: edgechromium, edgehtml, mshtml. mshtml is the only renderer that is guaranteed to be available on any system. Note that Edge Runtime must be installed in order to use Edge Chromium on Windows. You can download it from here. Distribution guidelines are found here.

To change a default renderer set either PYWEBVIEW_GUI environment variable or pass the rendered value to webview.start(gui=code) function parameter. Check for available values in the Code column from the table above.

For example to use CEF on Windows

PYWEBVIEW_GUI=cef

or

import webview
webview.start(gui='cef')

If you wish to pass custom settings to CEF, refer to this example

To force QT on Linux systems

PYWEBVIEW_GUI=qt

or

import webview
webview.start(gui='qt')

Known issues and limitations

GTK WebKit2

  • Versions of WebKit2 older than 2.2 has a limitation of 1000 characters of the Javascript result returned by evaluate_js. get_elements is not supported for this reason.

QtWebKit

  • Debugging is not supported

EdgeHTML

  • file:// URLs are not fully supported. While such URLs can be loaded, associated resources such as images or stylesheets cannot.
  • Destroying a window via window.destroy() and starting a new instance will crash the program.
  • Running the program under elevated privileges will throw an exception.
  • Access to localhost URLs is restricted by default. To overcome this the LoopbackExempt settings are modified on pywebview launch, which triggers a UAC prompt. This only happens once and only if LoopbackExempt setting is not set. You can manually set this setting beforehand to avoid UAC: checknetisolation LoopbackExempt -a -n="Microsoft.Win32WebViewHost_cw5n1h2txyewy" (must be run as an admin).