Blank window appears during WebView initialization

[nirdil]

What happened?

When initializing any WebView, a blank window briefly appears before disappearing.
This is most noticeable on app startup where the window can appear for a few seconds, but it is also noticeable sometimes very briefly on any new WebView initialization.

This seems to be a relatively recent bug that was introduced to the production Edge channel.

Additionally, this issue does not occur in the Edge Dev channel, which suggests it has been resolved in a later version. I’m unsure if this is a documented bug.

Can anyone confirm which version includes this fix and when it will be available in the production channel?

Importance

Important. My app's user experience is significantly compromised.

Runtime Channel

Stable release (WebView2 Runtime)

Runtime Version

129.0.2792.52

SDK Version

1.0.2839

Framework

WinUI2/UWP

Operating System

Windows 10

OS Version

10.0.19045

Repro steps

Not reproducible on a small sample project

Repros in Edge Browser

No, issue does not reproduce in the corresponding Edge version

Regression

Regression in newer Runtime

Last working version (if regression)

No response

AB#54137238

[naoki-yamamoto-ymh]

I have the same problem. Here is a sample code (omitted XAML / WinUI 3).

using Microsoft.UI.Xaml;
using Microsoft.Windows.AppLifecycle;
using System;
using System.Diagnostics;
using System.Threading;

namespace Sample {
    public partial class App: Application {
        private Window? window;

        public App() {
            InitializeComponent();
        }

        protected override async void OnLaunched(LaunchActivatedEventArgs args) {
            var main = AppInstance.FindOrRegisterForKey("main");
            if (main.IsCurrent) {
                window = new MainWindow {};
                window.Activate();

                // some heavy process.
                Thread.Sleep(2000);
            } else {
                await main.RedirectActivationToAsync(AppInstance.GetCurrent().GetActivatedEventArgs());
                try {
                    Process.GetCurrentProcess().Kill();
                } catch {
                }
            } 
        }
    }

    public sealed partial class MainWindow: Window {
        public MainWindow() {
            InitializeComponent();
            InitializeWebView();
        }

        private async void InitializeWebView() {
            await WebView.EnsureCoreWebView2Async();
            WebView.Source = new("https://example.com/");
        }
    }
}

capture.mp4

[champnic]

Thanks for opening this - I've added it as a bug on our side and we'll take a look right away. It's a good sign that it seems to be resolved in newer runtimes.

@naoki-yamamoto-ymh Are you able to see the issue in newer prerelease runtimes, like the current Dev channel?
https://learn.microsoft.com/en-us/microsoft-edge/webview2/how-to/set-preview-channel?tabs=api#downloading-the-prerelease-sdk-and-a-preview-channel

[naoki-yamamoto-ymh]

@champnic Thank you for your reply. I confirmed that this issue is resolved with Dev (130.0.2849.1) version!

[Thomr77]

Hi @champnic - We have the same issue with Maui Blazor Windows.

Is there a way for us to test this with a newer version as well? Maui references Windows App SDK (1.6) - not sure how to switch to a later WebView2?

Thanks!

[salvadordf]

I just got a report that this issue is also affecting WebView4Delphi developers.

[NicholasChrzan]

We are seeing this issue in our Win App SDK 1.4 and 1.6 based applications in already installed applications. It started showing up around 3-4 days ago. I'm guessing there was an update to the edge browser that started to cause this behavior.

[champnic]

@champnic Thank you for your reply. I confirmed that this issue is resolved with Dev (130.0.2849.1) version!

Thanks for confirming! 130 stable runtime should be deploying around mid-October.

Is there a way for us to test this with a newer version as well? Maui references Windows App SDK (1.6) - not sure how to switch to a later WebView2?

https://learn.microsoft.com/en-us/microsoft-edge/webview2/how-to/set-preview-channel?tabs=api#downloading-the-prerelease-sdk-and-a-preview-channel
You'll need to download a prerelease channel of the Edge browser (Canary or Dev), and then switch the runtime search order. Using the registry key or environment variable are probably the easiest here:
https://learn.microsoft.com/en-us/microsoft-edge/webview2/how-to/set-preview-channel?tabs=registry-key#switching-the-channel-search-order-recommended