cefsharp/CefSharp · error · Exception

Browser has not yet finished initializing or is being dispos

Error message

Browser has not yet finished initializing or is being disposed

What it means

Thrown by the example ChromiumWebBrowserWithScreenshotSupport.TakeScreenshot when IsBrowserInitialized is false. Capture works by resizing the off-screen browser and reading the rendered frame in OnPaint; if the browser has not finished initializing (or is being disposed) there is no renderer to produce a frame, so capture is rejected up front.

Source

Thrown at CefSharp.Wpf.Example/Controls/ChromiumWebBrowserWithScreenshotSupport.cs:56

        private CancellationTokenRegistration? cancellationTokenRegistration;

        public ICommand ScreenshotCommand { get; set; }

        public ChromiumWebBrowserWithScreenshotSupport() : base()
        {
            ScreenshotCommand = new RelayCommand(TakeScreenshot);
        }

        public Task<InteropBitmap> TakeScreenshot(Size screenshotSize, int? frameRate = 1, int? ignoreFrames = 0, CancellationToken? cancellationToken = null)
        {
            if (screenshotTaskCompletionSource != null && screenshotTaskCompletionSource.Task.Status == TaskStatus.Running)
            {
                throw new Exception("Screenshot already in progress, you must wait for the previous screenshot to complete");
            }

            if (IsBrowserInitialized == false)
            {
                throw new Exception("Browser has not yet finished initializing or is being disposed");
            }

            if (IsLoading)
            {
                throw new Exception("Unable to take screenshot while browser is loading");
            }

            var browserHost = this.GetBrowserHost();

            if (browserHost == null)
            {
                throw new Exception("IBrowserHost is null");
            }

            screenshotTaskCompletionSource = new TaskCompletionSource<InteropBitmap>(TaskCreationOptions.RunContinuationsAsynchronously);

            if (cancellationToken.HasValue)
            {

View on GitHub (pinned to 16bc6e0711)

Solutions

1. Wait until IsBrowserInitialized is true (subscribe to IsBrowserInitializedChanged or await initialization) before calling TakeScreenshot.
2. Guard with `if (browser.IsBrowserInitialized)` and disable the capture command until initialized.
3. Cancel any pending capture when the control starts disposing.
4. Ensure the browser has a loaded/committed page before capturing.

Example fix

// before
public MainWindow()
{
    browser = new ChromiumWebBrowserWithScreenshotSupport();
    var shot = browser.TakeScreenshot(size); // throws: not initialized
}

// after
browser.IsBrowserInitializedChanged += (s, e) =>
{
    if (browser.IsBrowserInitialized)
        _ = browser.TakeScreenshot(size);
};

if (browser.IsBrowserInitialized)
{
    _ = browser.TakeScreenshot(size);
}

When it happens

Trigger: Calling TakeScreenshot before the browser finished its initial creation; calling during shutdown while the browser is disposing.

Common situations: Wiring the screenshot to a window Loaded event that fires before CEF reports IsBrowserInitialized; capturing immediately after setting Address; capturing during app exit.

Related errors

• IBrowserHost is null
• Screenshot already in progress, you must wait for the previo
• Unable to take screenshot while browser is loading
• Browser has already been created. BrowserSettings must be se
• Browser has already been created. RequestContext must be set

AI-assisted analysis of cefsharp/CefSharp@16bc6e0711 (2026-08-13). Data as JSON: /api/errors/27a470d1c37aad21. Report an issue: GitHub.