CefSharp vs WebView2

Asked 15/12, 2021 at 8:2 Answered 8/1, 2023 at 1:27

Solved cefsharp chromium-embedded webview2

I'm considering moving a project from cef (CefSharp) to WebView2 WPF. My preliminary tests shows that WebView2 API have the interface I need for this port. I am afraid that I can miss something that can prevent me from switching to WebView2 and I'll figure this out at later stage of this transition. If anyone went through this process, please share if I need to be aware of something that can be a roadblock for this transition. Are there important APIs from cef that are missing in WebView2?

Pellegrini answered 15/12, 2021 at 8:2 Comment(1)

Try searching for: +CefSharp [WebView2] here on SO, that should give you questions and answers. – Albedo 15/12, 2021 at 8:18

This issue in WebView2's Github answers your question in part. And I would like to add my take.

A summary:

WebView2 doesn't have an API for simulating user input, it's unsuitable for automation.
WebView2 can't render offscreen. No running in the console, as a service, on a server.
WebView2 runs in a separate process; CefSharp runs in the application's process.
WebView2 has a sandbox; CefSharp doesn't.

This answer is based on my personal experience and is not an exhaustive comparison.

Process Model

The Chromium process model has the main process and many auxiliary processes. It is, of course, a bald simplification, but it will do.

Both CefSharp and WebView2 follow this process model with one very significant difference. CefSharp starts Chromium in the application's process, and WebView2 starts it as a separate process.

The in-process model is common to all CEF-based browsers. Pros: the browser starts faster. Cons:

If CEF crashes, it takes the application down with it.
If there's a vulnerability in CEF or Chromium, it can also expose the application's memory.

The out-of-process model is popular among proprietary browsers. Not only WebView2 works this way, but also DotNetBrowser and EO.WebBrowser. Pros:

It's safer.
It doesn't bite off the application's RAM. Cons:
It starts longer.
It may be slower because of inter-process communication.
Occasionally, there are issues with the focus and drag-and-drop because the browser window belongs to another process. Not applicable for the offscreen rendering, though.

CefSharp process model. WebView2 process model.

A score for WebView2.

Offscreen Rendering

There are two approaches to the rendering of embedded web content. One is to shake off the bells and whistles from an actual Chromium window and embed it into the application. We call this "windowed" or "heavyweight" mode. Another approach is to render web content in memory and draw it on an arbitrary surface. It's called "offscreen rendering."

WebView2 supports only windowed rendering. This mode has two significant drawbacks: it requires a window to function, and the browser always stays on top (aka the airspace issue).

CefSharp also has offscreen rendering. It allows the application to run in the console, overlay web content with other controls, render web content in Unity3D, etc.

A score for CefSharp.

Automation

The bread and butter of automation is simulating user input. CefSharp has an API for dispatching "real" mouse and keyboard events to the browser. The browser handles these events as user gestures, and JavaScript can't tell between them and real human input. Look at the SendMouse* and SendKey* methods in IBrowserHost.

There's no such API in WebView2, only workarounds based on Win API.

A score for CefSharp.

Sandbox

By default, all Chromium processes are sandboxed. It makes them more secure. The Chromium team explains the sandbox in great detail here.

WebView2 and other out-of-process libraries are sandboxed as well.

CefSharp doesn't support sandboxing and, it seems, never will (#697).

A score for WebView2.

License

CefSharp is open source, 3-BSD licensed. You can customise the code, fix bugs, submit pull requests, etc.

WebView2 is not currently open source. You need to wait for Microsoft to fix bugs. Currently WebView2 team releases updates every four weeks. Even if a bug is fixed quickly you can be waiting weeks before it's released.

Privacy

WebView2: Data collection privacy notice (at time of writing)

The software may collect information about you and your end users’ use of the software, and send that to Microsoft. Microsoft may use this information to provide services and improve our products and services. There are also some features in the software that may enable you to collect data from users of your applications. If you use these features to enable data collection in your applications, you must comply with applicable law, including providing appropriate notices to users of your applications. You can learn more about data collection and use in the help documentation and the privacy statement at https://aka.ms/privacy. Your use of the software operates as your consent to these practices.

Microsoft has yet to disclose exactly what is captured. Users must opt-out of data collection.

A number of users have raised concerns regarding the data telemetry. There are a number of discussions regarding the privacy concerns here and here.

Distribution Model

Both CefSharp and WebView2 require a specialised version of Chromium to be installed/copied on your computer.

Fixed Version: A fixed version of Chromium is bundled with your application. You control which version. Evergreen: Chromium is is installed then automatically updated via windows update. On some OS's it will be pre-installed. Currently limited/no control over if the runtime is updated.

	CefSharp	WebView2
Fixed	[x]	[x]
Evergreen		[x]

Chromium is rapidly changing, there's a new major version every four weeks at time of writing. Each major release adds/removes features. Security policies are changed. What worked flawlessly on a previous version of Chromium may no longer be allowed for security reasons. Deprecated features are frequently removed.

For complex applications it's important/imperative to tested against the specific version of Chromium your application uses. This applies to all Chromium based browser.

Evergreen WebView2 Runtime automatically updated via Windows Update sounds perfect? Get the latest version without having to do everything. What happens when a bug makes it into a Stable Release? Did you test your application against the dev/beta channels to flag upcoming issues? No? You could be inundated with user complaints their application now crashes.

A quick look though the WebView2Feedback Issue Tracker and you can see examples of this happening.

M108 release was particularly problematic with many users reporting issues. The following are just some examples

For those using an Evergreen model you must test your application on every dev/beta release to ensure your application works as expected.

WPF

CefSharp provides two WPF implementations, the first CefSharp.Wpf renders every frame to a bitmap, this allows for a native WPF experience. You can apply transforms, layer elements over the top, etc. There are no airspace issues. There are a few downsides the main being performance is lower (there are a few things you can do to squeeze some extra frames). The second is CefSharp.Wpf.HwndHost, it's a HwndHost based implementation, it's like embedding the WinForms version in WPF with binding support, you get much better performance, no transforms, cannot layer over the top. Airspace issues apply.

WebView2 currently only provides a HwndHost implementation, airspace issues apply. There is talk of providing a more native WPF implementation

Daffie answered 8/1, 2023 at 1:27 Comment(1)

It looks like the 'evergreen' runtime is automatically installed in Windows 11, and perhaps also in Windows 10 as part of newer .NET Desktop Runtimes. – Balliett 13/3 at 17:31