interface ICoreWebView2ExperimentalEnvironment4


This an experimental API that is shipped with our prerelease SDK. See WebView2 release notes.

interface ICoreWebView2ExperimentalEnvironment4
  : public IUnknown

This interface is an extension of the ICoreWebView2Environment that supports BrowserProcessExited event.


Members Descriptions
add_BrowserProcessExited Add an event handler for the BrowserProcessExited event.
remove_BrowserProcessExited Remove an event handler previously added with add_BrowserProcessExited.

An object implementing the ICoreWebView2ExperimentalEnvironment4 interface will also implement ICoreWebView2Environment.

Applies to

Product Introduced
WebView2 Win32 N/A
WebView2 Win32 Prerelease 1.0.902



Add an event handler for the BrowserProcessExited event.

public HRESULT add_BrowserProcessExited(ICoreWebView2ExperimentalBrowserProcessExitedEventHandler * eventHandler, EventRegistrationToken * token)

The BrowserProcessExited event is raised when the collection of WebView2 Runtime processes for the browser process of this environment terminate due to browser process failure or normal shutdown (for example, when all associated WebViews are closed), after all resources have been released (including the user data folder). To learn about what these processes are, go to Process model.

A handler added with this method is called until removed with remove_BrowserProcessExited, even if a new browser process is bound to this environment after earlier BrowserProcessExited events are raised.

Multiple app processes can share a browser process by creating their webviews from a ICoreWebView2Environment with the same user data folder. When the entire collection of WebView2Runtime processes for the browser process exit, all associated ICoreWebView2Environment objects receive the BrowserProcessExited event. Multiple processes sharing the same browser process need to coordinate their use of the shared user data folder to avoid race conditions and unnecessary waits. For example, one process should not clear the user data folder at the same time that another process recovers from a crash by recreating its WebView controls; one process should not block waiting for the event if other app processes are using the same browser process (the browser process will not exit until those other processes have closed their webviews too).

Note this is an event from the ICoreWebView2Environment3 interface, not the ICoreWebView2 one. The difference between BrowserProcessExited and ICoreWebView2's ProcessFailed is that BrowserProcessExited is raised for any browser process exit (expected or unexpected, after all associated processes have exited too), while ProcessFailed is raised for unexpected process exits of any kind (browser, render, GPU, and all other types), or for main frame render process unresponsiveness. To learn more about the WebView2 Process Model, go to Process model.

In the case the browser process crashes, both BrowserProcessExited and ProcessFailed events are raised, but the order is not guaranteed. These events are intended for different scenarios. It is up to the app to coordinate the handlers so they do not try to perform reliability recovery while also trying to move to a new WebView2 Runtime version or remove the user data folder.

// Close the WebView and deinitialize related state. This doesn't close the app window.
void AppWindow::CloseWebView(bool cleanupUserDataFolder)
    // 1. Delete components.

    // 2. If cleanup needed and BrowserProcessExited event interface available,
    // register to cleanup upon browser exit.
    wil::com_ptr<ICoreWebView2ExperimentalEnvironment4> experimentalEnvironment4;
    if (m_webViewEnvironment)
        experimentalEnvironment4 =
    if (cleanupUserDataFolder && experimentalEnvironment4)
        // Before closing the WebView, register a handler with code to run once the
        // browser process and associated processes are terminated.
                [experimentalEnvironment4, this](
                    ICoreWebView2Environment* sender,
                    ICoreWebView2ExperimentalBrowserProcessExitedEventArgs* args) {
                    UINT32 pid;

                    // If a new WebView is created from this CoreWebView2Environment after
                    // the browser has exited but before our handler gets to run, a new
                    // browser process will be created and lock the user data folder
                    // again. Do not attempt to cleanup the user data folder in these
                    // cases. We check the PID of the exited browser process against the
                    // PID of the browser process to which our last CoreWebView2 attached.
                    if (pid == m_newestBrowserPid)
                        // Watch for graceful browser process exit. Let ProcessFailed event
                        // handler take care of failed browser process termination.
                        if (kind == COREWEBVIEW2_BROWSER_PROCESS_EXIT_KIND_NORMAL)
                            // Release the environment only after the handler is invoked.
                            // Otherwise, there will be no environment to raise the event when
                            // the collection of WebView2 Runtime processes exit.
                            m_webViewEnvironment = nullptr;
                        // The exiting process is not the last in use. Do not attempt cleanup
                        // as we might still have a webview open over the user data folder.
                        // Do not block from event handler.
                        RunAsync([this]() {
                                L"A new browser process prevented cleanup of the user data folder.",
                                L"Cleanup User Data Folder", MB_OK);

                    return S_OK;

    // 3. Close the webview.
    if (m_controller)
        m_controller = nullptr;
        m_webView = nullptr;
        m_webView3 = nullptr;

    // 4. If BrowserProcessExited event interface is not available, release
    // environment and proceed to cleanup immediately. If the interface is
    // available, release environment only if not waiting for the event.
    if (!experimentalEnvironment4)
        m_webViewEnvironment = nullptr;
        if (cleanupUserDataFolder)
    else if (!cleanupUserDataFolder)
        // Release the environment object here only if no cleanup is needed.
        // If cleanup is needed, the environment object release is deferred
        // until the browser process exits, otherwise the handler for the
        // BrowserProcessExited event will not be called.
        m_webViewEnvironment = nullptr;


Remove an event handler previously added with add_BrowserProcessExited.

public HRESULT remove_BrowserProcessExited(EventRegistrationToken token)