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Extensions.md

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Background

Developers would like to ensure a browser extension is installed so that they may take advantage of the functionality the extension is providing.

Description

Enable extension services in WebView2. Then end developer can AddBrowserExtension from folder path, GetBrowserExtensions to get list of extensions installed. Once an extension is installed, developers can use ICoreWebView2BrowserExtension to get id, name of this extension. And also remove or enable/disable this extension.

Examples

The following code snippet demonstrates how the Extensions related API can be used:

Install extension on first run

You may have a browser extension that is specific to your application's web content. This snippet shows how you can install your browser extension on your first run.

Win32 C++

// m_defaultExtensionFolderPath need to match the path of the package you want to install
std::wstring m_defaultExtensionFolderPath = L"C:/MyProject/extensions/example-extension";

void AppWindow::InitializeWebView()
{
    auto options = Microsoft::WRL::Make<CoreWebView2EnvironmentOptions>();
    CHECK_FAILURE(options->put_AreBrowserExtensionsEnabled(TRUE));

    // ... other option properties

    // ... CreateCoreWebView2EnvironmentWithOptions

    bool installed = InstallDefaultExtensions();

    if (installed)
    {
        // ... Show app content
    }
}

bool void ScenarioExtensionsManagement::InstallDefaultExtensions()
{
    auto webView2_13 = m_webView.try_query<ICoreWebView2_13>();
    CHECK_FEATURE_RETURN_EMPTY(webView2_13);
    wil::com_ptr<ICoreWebView2Profile> webView2Profile;
    CHECK_FAILURE(webView2_13->get_Profile(&webView2Profile));
    auto profile6 = webView2Profile.try_query<ICoreWebView2Profile6>();
    CHECK_FEATURE_RETURN_EMPTY(profile6);

    CHECK_FAILURE(profile6->GetBrowserExtensions(
        Callback<ICoreWebView2ProfileGetBrowserExtensionCompletedHandler>(
            [this, profile6](
                HRESULT error, ICoreWebView2BrowserExtensionList* extensions) -> HRESULT noexcept
            {
                if (error != S_OK)
                {
                    UINT extensionsCount = 0;
                    CHECK_FAILURE(extensions->get_Count(&extensionsCount));
                    assert(extensionsCount == 0);
                    
                    ShowFailure(error, L"GetBrowserExtensions failed");
                    return S_OK;
                }
                std::wstring extensionIdString;
                bool extensionInstalled = false;
                UINT extensionsCount = 0;
                CHECK_FAILURE(extensions->get_Count(&extensionsCount));

                for (UINT index = 0; index < extensionsCount; ++index)
                {
                    wil::com_ptr<ICoreWebView2BrowserExtension> extension;
                    CHECK_FAILURE(extensions->GetValueAtIndex(index, &extension));

                    wil::unique_cotaskmem_string id;

                    CHECK_FAILURE(extension->get_Id(&id));
                    extensionIdString = id.get();

                    if (extensionIdString.compare(m_extensionId) == 0)
                    {
                        extensionInstalled = true;
                        break;
                    }
                }

                if (!extensionInstalled)
                {
                    CHECK_FAILURE(profile6->AddBrowserExtension(
                        m_defaultExtensionFolderPath.c_str(),
                        Callback<ICoreWebView2ProfileAddBrowserExtensionCompletedHandler>(
                            [](HRESULT error,
                               ICoreWebView2BrowserExtension* extension) -> HRESULT
                            {
                                if (error != S_OK)
                                {
                                    ShowFailure(error, L"AddExtension failed");
                                    return S_OK;
                                }
                                return S_OK;
                            })
                            .Get()));
                }
                return S_OK;
            })
            .Get()));
    return extensionInstalled;
}

.NET and WinRT

// m_defaultExtensionId need to match the package ID you want to install
string m_defaultExtensionId = "apaahjmopbjicnjjcnionchiganhjpcd";
// m_defaultExtensionFolderPath need to match the path of the package you want to install
string m_defaultExtensionFolderPath = "C:/MyProject/extensions/example-extension";

/// Create WebView Environment with option
async void CreateEnvironmentWithOption()
{
    CoreWebView2EnvironmentOptions options = new CoreWebView2EnvironmentOptions();
    options.AreBrowserExtensionsEnabled = true;
    CoreWebView2Environment environment = await CoreWebView2Environment.CreateAsync(options: options);
    webview.EnsureCoreWebView2Async(environment);

    await InstallDefaultExtensions();
}

// Install default extension before first navigation
private async System.Threading.Tasks.Task InstallDefaultExtensions()
{
    List<CoreWebView2BrowserExtension> extensionsList = await m_coreWebView2.Profile.GetBrowserExtensionsAsync();
    bool found = extensionsList.Any(extension => extension.Id == m_defaultExtensionId);
    if (!found)
    {
        await m_coreWebView2.Profile.AddBrowserExtensionAsync(m_defaultExtensionFolderPath);
    }
}

End user manages extensions

Provide end user the ability to add, remove, enable and disable a browser extension from profile.

Win32 C++

void AsyncMessageBox(std::wstring message, std::wstring title)
{
    RunAsync([this, message = std::move(message), title = std::move(title)]
             { MessageBox(nullptr, message.c_str(), title.c_str(), MB_OK); });
}

void BrowserExtensionService::AddBrowserExtension()
{

    // Get the profile object.
    auto webView2_13 = m_webView.try_query<ICoreWebView2_13>();
    wil::com_ptr<ICoreWebView2Profile> webView2Profile;
    CHECK_FAILURE(webView2_13->get_Profile(&webView2Profile));
    auto profile6 = webView2Profile.try_query<ICoreWebView2Profile6>();

    OPENFILENAME openFileName = {};
    openFileName.lStructSize = sizeof(openFileName);
    openFileName.hwndOwner = nullptr;
    openFileName.hInstance = nullptr;
    WCHAR fileName[MAX_PATH] = L"";
    openFileName.lpstrFile = fileName;
    openFileName.lpstrFilter = L"Manifest\0manifest.json\0\0";
    openFileName.nMaxFile = ARRAYSIZE(fileName);
    openFileName.Flags = OFN_OVERWRITEPROMPT;

    if (GetOpenFileName(&openFileName))
    {
        // Remove the filename part of the path.
        *wcsrchr(fileName, L'\\') = L'\0';
        CHECK_FAILURE(profile6->AddBrowserExtension(
            fileName,
            Callback<ICoreWebView2ProfileAddBrowserExtensionCompletedHandler>(
                [](HRESULT error, ICoreWebViewBrowserExtension* extension) -> HRESULT
                {
                    if (error != S_OK)
                    {
                        ShowFailure(error, L"Failed to add extension");
                        return S_OK;
                    }
                    wil::unique_cotaskmem_string id;
                    CHECK_FAILURE(extension->get_Id(&id));

                    wil::unique_cotaskmem_string name;
                    CHECK_FAILURE(extension->get_Name(&name));

                    std::wstring extensionInfo;
                    extensionInfo.append(L"Added extension ");
                    extensionInfo.append(name.get());
                    extensionInfo.append(L" (");
                    extensionInfo.append(id.get());
                    extensionInfo.append(L")");
                    AsyncMessageBox(std::move(extensionInfo.str()), L"AddBrowserExtension Result");
                    return S_OK;
                })
                .Get()));
    }
}

void BrowserExtensionService::RemoveExtension()
{
    // Get the profile object.
    auto webView2_13 = m_webView.try_query<ICoreWebView2_13>();
    wil::com_ptr<ICoreWebView2Profile> webView2Profile;
    CHECK_FAILURE(webView2_13->get_Profile(&webView2Profile));
    auto profile6 = webView2Profile.try_query<ICoreWebView2Profile6>();

    CHECK_FAILURE(profile6->GetExtensions(
        Callback<ICoreWebView2ProfileGetBrowserExtensionCompletedHandler>(
            [this](HRESULT error, ICoreWebView2BrowserExtensionList* extensions) -> HRESULT
            {
                AppWindow* appWindow = m_appWindow;
                wil::com_ptr<ICoreWebView2StagingExtensionList> extensionList = extensions;
                appWindow->RunAsync(
                    [appWindow, extensionIdString, extensionList]
                    {
                        TextInputDialog dialog(
                            m_appWindow->GetMainWindow(), L"Remove Extension",
                            L"Extension ID:", extensionIdString.c_str());
                        UINT extensionsCount = 0;
                        CHECK_FAILURE(extensions->get_Count(&extensionsCount));
                        
                        if (dialog.confirmed)
                        {
                            for (UINT index = 0; index < extensionsCount; ++index)
                            {
                                wil::com_ptr<ICoreWebView2BrowserExtension> extension;
                                CHECK_FAILURE(extensions->GetValueAtIndex(index, &extension));

                                wil::unique_cotaskmem_string id;
                                wil::unique_cotaskmem_string name;

                                CHECK_FAILURE(extension->get_Id(&id));
                                if (_wcsicmp(id.get(), dialog.input.c_str()) == 0)
                                {
                                    // If there are multiple apps or threads using the same profile,
                                    // these instance need to coordinate themselves to avoid double deleting.
                                    CHECK_FAILURE(extension->Remove(
                                        Callback<ICoreWebView2BrowserExtensionRemoveCompletedHandler>(
                                            [](HRESULT error) -> HRESULT
                                            {
                                                if (error != S_OK)
                                                {
                                                    ShowFailure(error, L"Failed to remove extension from profile.");
                                                    return S_OK;
                                                }
                                                AsyncMessageBox(L"Done", L"Remove Extension");
                                                return S_OK;
                                            })
                                            .Get()));
                                }
                            }
                        }
                });
                return S_OK;
            })
            .Get()));
}

void BrowserExtensionService::ToggleExtensionEnabled()
{
    // Get the profile object.
    auto webView2_13 = m_webView.try_query<ICoreWebView2_13>();
    wil::com_ptr<ICoreWebView2Profile> webView2Profile;
    CHECK_FAILURE(webView2_13->get_Profile(&webView2Profile));
    auto profile6 = webView2Profile.try_query<ICoreWebView2Profile6>();

    CHECK_FAILURE(profile6->GetExtensions(
        Callback<ICoreWebView2ProfileGetBrowserExtensionCompletedHandler>(
            [this](HRESULT error, ICoreWebView2BrowserExtensionList* extensions) -> HRESULT
            {
                AppWindow* appWindow = m_appWindow;
                wil::com_ptr<ICoreWebView2StagingExtensionList> extensionList = extensions;
                appWindow->RunAsync(
                    [appWindow, extensionIdString, extensionList]
                    {
                        TextInputDialog dialog(
                            m_appWindow->GetMainWindow(), L"Disable/Enable Extension",
                            L"Extension ID:", extensionIdString.c_str());
                        UINT extensionsCount = 0;
                        CHECK_FAILURE(extensionList->get_Count(&extensionsCount));
                        
                        if (dialog.confirmed)
                        {
                            for (UINT index = 0; index < extensionsCount; ++index)
                            {
                                wil::com_ptr<ICoreWebView2BrowserExtension> extension;
                                CHECK_FAILURE(extensions->GetValueAtIndex(index, &extension));

                                wil::unique_cotaskmem_string id;
                                wil::unique_cotaskmem_string name;

                                CHECK_FAILURE(extension->get_Id(&id));
                                if (_wcsicmp(id.get(), dialog.input.c_str()) == 0)
                                {
                                    BOOL enabled = FALSE;
                                    CHECK_FAILURE(extension->get_IsEnabled(&enabled));

                                    CHECK_FAILURE(extension->Enable(
                                        !enabled,
                                        Callback<ICoreWebView2BrowserExtensionEnabledCompletedHandler>(
                                            [](HRESULT error) -> HRESULT
                                            {
                                                if (error != S_OK)
                                                {
                                                    ShowFailure(
                                                        error, L"Enable Extension failed");
                                                    return S_OK;
                                                }
                                                AsyncMessageBox(L"Done", L"Toggled Extension");
                                                return S_OK;
                                            })
                                            .Get()));
                                }
                            }
                        }
                    });
                return S_OK;
            })
            .Get()));
}

.NET and WinRT

// Extensions class
/// <summary>
/// Interaction logic for Extensions.xaml
/// </summary>
public partial class Extensions : Window
{
    private CoreWebView2 m_coreWebView2;
    public Extensions(CoreWebView2 coreWebView2)
    {
        m_coreWebView2 = coreWebView2;
        InitializeComponent();
        _ = FillViewAsync();
    }

    public class ListEntry
    {
        public string Name;
        public string Id;
        public bool Enabled;

        public override string ToString()
        {
            return (Enabled ? "" : "Disabled ") + Name + " (" + Id + ")";
        }
    }

    List<ListEntry> m_listData = new List<ListEntry>();

    private async System.Threading.Tasks.Task FillViewAsync()
    {
        List<CoreWebView2BrowserExtension> extensionsList = await m_coreWebView2.Profile.GetBrowserExtensionsAsync();

        m_listData.Clear();
        for (int i = 0; i < extensionsList.Count; ++i)
        {
            ListEntry entry = new ListEntry();
            entry.Name = extensionsList[i].Name;
            entry.Id = extensionsList[i].Id;
            entry.Enabled = extensionsList[i].IsEnabled;
            m_listData.Add(entry);
        }
        ExtensionsList.ItemsSource = m_listData;
        ExtensionsList.Items.Refresh();
    }

    private void AddBrowserExtension(object sender, RoutedEventArgs e)
    {
        _ = AddBrowserExtensionAsync(sender, e);
    }

    private async System.Threading.Tasks.Task AddBrowserExtensionAsync(object sender, RoutedEventArgs e)
    {
        var dialog = new TextInputDialog(
            title: "Add extension",
            description: "Enter the absolute Windows file path to the unpackaged browser extension",
            defaultInput: "");
        if (dialog.ShowDialog() == true)
        {
            try
            {
                CoreWebView2Extension extension = await m_coreWebView2.Profile.AddBrowserExtensionAsync(dialog.Input.Text);
                MessageBox.Show("Added extension " + extension.Name + " (" + extension.Id + ")");
                await FillViewAsync();
            }
            catch (Exception exception)
            {
                MessageBox.Show("Failed to add extension: " + exception);
            }
        }
    }

    private void RemoveExtension(object sender, RoutedEventArgs e)
    {
        _ = RemoveExtensionAsync(sender, e);
    }

    private async System.Threading.Tasks.Task RemoveExtensionAsync(object sender, RoutedEventArgs e)
    {
        ListEntry entry = (ListEntry)ExtensionsList.SelectedItem;
        if (MessageBox.Show("Remove extension " + entry + "?", "Confirm removal", MessageBoxButton.OKCancel) == MessageBoxResult.OK)
        {
            List<CoreWebView2BrowserExtension> extensionsList = await m_coreWebView2.Profile.GetBrowserExtensionsAsync();
            for (int i = 0; i < extensionsList.Count; ++i)
            {
                if (extensionsList[i].Id == entry.Id)
                {
                    try
                    {
                        await extensionsList[i].RemoveAsync();
                    }
                    catch (Exception exception)
                    {
                        MessageBox.Show("Failed to remove extension: " + exception);
                    }
                    break;
                }
            }
        }
        await FillViewAsync();
    }

    private void ToggleExtensionEnabled(object sender, RoutedEventArgs e)
    {
        _ = ToggleExtensionEnabledAsync(sender, e);
    }

    private async System.Threading.Tasks.Task ToggleExtensionEnabledAsync(object sender, RoutedEventArgs e)
    {
        ListEntry entry = (ListEntry)ExtensionsList.SelectedItem;
        List<CoreWebView2BrowserExtension> extensionsList = await m_coreWebView2.Profile.GetBrowserExtensionsAsync();
        for (int i = 0; i < extensionsList.Count; ++i)
        {
            if (extensionsList[i].Id == entry.Id)
            {
                try
                {
                    await extensionsList[i].EnableAsync(extensionsList[i].IsEnabled ? false : true);
                }
                catch (Exception exception)
                {
                    MessageBox.Show("Failed to toggle extension enabled: " + exception);
                }
                break;
            }
        }
        await FillViewAsync();
    }
}

API Notes

See API Details section below for API reference.

API Details

Win32 C++

interface ICoreWebView2Profile6;
interface ICoreWebView2EnvironmentOptions6;
interface ICoreWebView2BrowserExtensionEnabledCompletedHandler;
interface ICoreWebView2BrowserExtensionRemoveCompletedHandler;
interface ICoreWebView2BrowserExtension;
interface ICoreWebView2BrowserExtensionList;
interface ICoreWebView2ProfileAddBrowserExtensionCompletedHandler;
interface ICoreWebView2ProfileGetBrowserExtensionsCompletedHandler;

/// Additional options used to create WebView2 Environment.
[uuid(4B1F63E9-F7A5-4EA5-8D84-2B30F2404E82), object, pointer_default(unique)]
interface ICoreWebView2EnvironmentOptions6 : ICoreWebView2EnvironmentOptions5 {
  /// When `AreBrowserExtensionsEnabled` is set to `TRUE`, new extensions can be added to user 
  /// profile and used. `AreBrowserExtensionsEnabled` is default to be `FALSE`, in this case,
  /// new extensions can't be installed, and already installed extension won't be 
  /// available to use in user profile.
  /// If connecting to an already running environment with a different value for `AreBrowserExtensionsEnabled`
  /// property, it will fail with `HRESULT_FROM_WIN32(ERROR_INVALID_STATE)`.
  /// See `ICoreWebView2BrowserExtension` for Extensions API details.
  [propget] HRESULT AreBrowserExtensionsEnabled([out, retval] BOOL* value);
  /// Sets the `AreBrowserExtensionsEnabled` property.
  [propput] HRESULT AreBrowserExtensionsEnabled([in] BOOL value);
}

/// This is the ICoreWebView2 profile.
[uuid(8B16D238-9508-4C36-B4D4-749EB9AC4AD0), object, pointer_default(unique)]
interface ICoreWebView2Profile6 : IUnknown {
    /// Adds the [browser extension](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions) 
    /// using the extension path for unpacked extensions from the local device. Extension is 
    /// running right after installation.
    /// The extension folder path is the topmost folder of an unpacked browser extension and 
    /// contains the browser extension manifest file.
    /// If the `extensionFolderPath` is an invalid path or doesn't contain the extension manifest.json
    /// file, this function will return `ERROR_FILE_NOT_FOUND` to callers. 
    /// Installed extension will default `IsEnabled` to true.
    /// When `AreBrowserExtensionsEnabled` is `FALSE`, `AddBrowserExtension` will fail and return 
    /// HRESULT `ERROR_NOT_SUPPORTED`.
    /// During installation, the content of the extension is not copied to the user data folder. 
    /// Once the extension is installed, changing the content of the extension will cause the 
    /// extension to be removed from the installed profile. 
    /// When an extension is added the extension is persisted in the corresponding profile. The 
    /// extension will still be installed the next time you use this profile.
    /// When an extension is installed from a folder path, adding the same extension from the same
    /// folder path means reinstalleing this extension. When two extensions with the same Id are 
    /// installed, only the later installed extension will be kept.
    /// 
    /// The following summarizes the possible error values that can be returned from 
    /// `AddBrowserExtension` and a description of why these errors occur.
    ///
    /// Error value                                     | Description
    /// ----------------------------------------------- | --------------------------
    /// `HRESULT_FROM_WIN32(ERROR_NOT_SUPPORTED)`       | Extensions are disabled.
    /// `HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND)`      | Cannot find `manifest.json` file or it is not a valid extension manifest.
    /// `E_ACCESSDENIED`                                | Cannot load extension with file or directory name starting with \"_\", reserved for use by the system.
    /// `E_FAIL`                                        | Extension failed to install with other unknown reasons. 
    HRESULT AddBrowserExtension([in] LPCWSTR extensionFolderPath, [in] ICoreWebView2ProfileAddBrowserExtensionCompletedHandler* handler);
    /// Gets a snapshot of the set of extensions installed at the time `GetBrowserExtensions` is 
    /// called. If an extension is installed or uninstalled after `GetBrowserExtensions` completes, 
    /// the list returned by `GetBrowserExtensions` remains the same.
    /// When `AreBrowserExtensionsEnabled` is `FALSE`, `GetBrowserExtensions` won't return any 
    /// extensions on current user profile.
    HRESULT GetBrowserExtensions([in] ICoreWebView2ProfileGetBrowserExtensionsCompletedHandler* handler);
}

/// Provides a set of properties for managing an Extension, which includes
/// an ID, name, and whether it is enabled or not, and the ability to Remove
/// the Extension, and enable or disable it.
[uuid(BCFC3E36-1BAD-4009-BFFC-A372C469F6BA), object, pointer_default(unique)]
interface ICoreWebView2BrowserExtension : IUnknown {
    /// This is the browser extension's ID. This is the same browser extension ID returned by 
    /// the browser extension API [`chrome.runtime.id`](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/runtime/id). 
    /// Please see that documentation for more details on how the ID is generated.
    /// After an extension is removed, calling `Id` will return the id of the extension that is removed.
    /// The caller must free the returned string with `CoTaskMemFree`.  See
    /// [API Conventions](/microsoft-edge/webview2/concepts/win32-api-conventions#strings).
    [propget] HRESULT Id([out, retval] LPWSTR* value); 
    /// This is the browser extension's name. This value is defined in this browser extension's 
    /// manifest.json file. If manifest.json define extension's localized name, this value will 
    /// be the localized version of the name.
    /// Please see [Manifest.json name](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/name) 
    /// for more details.
    /// After an extension is removed, calling `Name` will return the name of the extension that is removed.
    /// The caller must free the returned string with `CoTaskMemFree`.  See
    /// [API Conventions](/microsoft-edge/webview2/concepts/win32-api-conventions#strings).
    [propget] HRESULT Name([out, retval] LPWSTR* value);
    /// Removes this browser extension from its WebView2 Profile. The browser extension is removed 
    /// immediately including from all currently running HTML documents associated with this 
    /// WebView2 Profile. The removal is persisted and future uses of this profile will not have this 
    /// extension installed. After an extension is removed, calling `Remove` again will cause an exception.
    HRESULT Remove([in] ICoreWebView2BrowserExtensionRemoveCompletedHandler* handler);
    /// If `isEnabled` is true then the Extension is enabled and running in WebView instances.
    /// If it is false then the Extension is disabled and not running in WebView instances.
    /// When a Extension is first installed, `IsEnable` are default to be `TRUE`.
    /// `isEnabled` is persisted per profile.
    /// After an extension is removed, calling `isEnabled` will return the value at the time it was removed.
    [propget] HRESULT IsEnabled([out, retval] BOOL* value);
    /// Sets whether this browser extension is enabled or disabled. This change applies immediately 
    /// to the extension in all HTML documents in all WebView2s associated with this profile.
    /// After an extension is removed, calling `Enable` will not change the value of `IsEnabled`.
    HRESULT Enable([in] BOOL isEnabled, [in] ICoreWebView2BrowserExtensionEnabledCompletedHandler* handler);
}

/// Provides a set of properties for managing browser Extension Lists from user profile. This
/// includes the number of browser Extensions in the list, and the ability to get an browser 
/// Extension from the list at a particular index.
[uuid(59251055-F2F1-448F-A096-F996FB9ACBE2), object, pointer_default(unique)]
interface ICoreWebView2BrowserExtensionList : IUnknown {
    /// The number of browser Extensions in the list.
    [propget] HRESULT Count([out, retval] UINT* count);
    /// Gets the browser Extension located in the browser Extension List at the given index.
    HRESULT GetValueAtIndex([in] UINT index, [out, retval] ICoreWebView2BrowserExtension** extension);
}

/// The caller implements this interface to receive the result of
/// getting the browser Extensions.
[uuid(2A05565F-DE9D-46E3-AAF7-B866966828F4), object, pointer_default(unique)]
interface ICoreWebView2ProfileGetBrowserExtensionsCompletedHandler : IUnknown {
    HRESULT Invoke([in] HRESULT errorCode, [in] ICoreWebView2BrowserExtensionList* extensionList);
}

/// The caller implements this interface to receive the result
/// of loading an browser Extension.
[uuid(E81499FE-8BC6-4BA6-BAD7-D21FFA4C3266), object, pointer_default(unique)]
interface ICoreWebView2ProfileAddBrowserExtensionCompletedHandler : IUnknown {
    HRESULT Invoke([in] HRESULT errorCode, [in] ICoreWebView2BrowserExtension* extension);
}

/// The caller implements this interface to receive the result of removing
/// the browser Extension from the Profile.
[uuid(BD73ED6B-08A3-4A57-9DD0-2903067632B4), object, pointer_default(unique)]
interface ICoreWebView2BrowserExtensionRemoveCompletedHandler : IUnknown {
    HRESULT Invoke([in] HRESULT errorCode);
}

/// The caller implements this interface to receive the result of setting the
/// browser Extension as enabled or disabled. If enabled, the browser Extension is 
/// running in WebView instances. If disabled, the browser Extension is not running in WebView instances.
[uuid(0A5F7098-2265-49C7-BA60-5A511E80805A), object, pointer_default(unique)]
interface ICoreWebView2BrowserExtensionEnabledCompletedHandler : IUnknown {
    HRESULT Invoke([in] HRESULT errorCode);
}

.NET and WinRT

namespace Microsoft.Web.WebView2.Core
{
    
    // ...
    runtimeclass CoreWebView2BrowserExtension;
    
    // ...
    runtimeclass CoreWebView2EnvironmentOptions
    {
        // ...
        Boolean AreBrowserExtensionsEnabled { get; set; };
    }

    // ...
    runtimeclass CoreWebView2Profile
    {
        // ...
        Windows.Foundation.IAsyncOperation<CoreWebView2BrowserExtension> AddBrowserExtensionAsync(String extensionFolderPath);
        IAsyncOperation<IVectorView<CoreWebView2BrowserExtension>> GetBrowserExtensionsAsync();
    }

    runtimeclass CoreWebView2BrowserExtension
    {
        String Id { get; };
        String Name { get; };
        Boolean IsEnabled { get; };
        Windows.Foundation.IAsyncAction RemoveAsync();
        Windows.Foundation.IAsyncAction EnableAsync(Boolean isEnabled);
    }

    // ...
}