Browsers used by Office Add-ins

Office Add-ins are web applications that are displayed using iFrames when running in Office on the web. In Office for desktop and mobile clients, Office Add-ins use an embedded browser control (also known as a webview). Add-ins also need a JavaScript engine to run the JavaScript. Both the embedded browser and the engine are supplied by a browser installed on the user's computer.

Which browser is used depends on:

  • The computer's operating system.
  • Whether the add-in is running in Office on the web, Microsoft 365, or non-subscription Office 2013 or later.


Internet Explorer still used in Office Add-ins

Some combinations of platforms and Office versions, including one-time-purchase versions through Office 2019, still use the webview control that comes with Internet Explorer 11 to host add-ins, as explained in this article. We recommend (but don't require) that you continue to support these combinations, at least in a minimal way, by providing users of your add-in a graceful failure message when your add-in is launched in the Internet Explorer webview. Keep these additional points in mind:

  • Office on the web no longer opens in Internet Explorer. Consequently, AppSource no longer tests add-ins in Office on the web using Internet Explorer as the browser.
  • AppSource still tests for combinations of platform and Office desktop versions that use Internet Explorer, however it only issues a warning when the add-in does not support Internet Explorer; the add-in is not rejected by AppSource.
  • The Script Lab tool no longer supports Internet Explorer.

For more information about supporting Internet Explorer and configuring a graceful failure message on your add-in, see Support Internet Explorer 11.

The following table shows which browser is used for the various platforms and operating systems.

OS Office version Edge WebView2 (Chromium-based) installed? Browser
any Office on the web Not applicable The browser in which Office is opened.
(But note that Office on the web will not open in Internet Explorer.
Attempting to do so opens Office on the web in Edge.)
Mac any Not applicable Safari with WKWebView
iOS any Not applicable Safari with WKWebView
Android any Not applicable Chrome
Windows 7, 8.1, 10, 11 non-subscription Office 2013 to Office 2019 Doesn't matter Internet Explorer 11
Windows 10, 11 non-subscription Office 2021 or later Yes Microsoft Edge1 with WebView2 (Chromium-based)
Windows 7 Microsoft 365 Doesn't matter Internet Explorer 11
Windows 8.1,
Windows 10 ver. < 1903
Microsoft 365 No Internet Explorer 11
Windows 10 ver. >= 1903,
Windows 11
Microsoft 365 ver. < 16.0.116292 Doesn't matter Internet Explorer 11
Windows 10 ver. >= 1903,
Windows 11
Microsoft 365 ver. >= 16.0.11629 AND < 16.0.13530.204242 Doesn't matter Microsoft Edge1, 3 with original WebView (EdgeHTML)
Windows 10 ver. >= 1903,
Window 11
Microsoft 365 ver. >= 16.0.13530.204242 No Microsoft Edge1, 3 with original WebView (EdgeHTML)
Windows 8.1
Windows 10,
Windows 11
Microsoft 365 ver. >= 16.0.13530.204242 Yes4 Microsoft Edge1 with WebView2 (Chromium-based)

1 When Microsoft Edge is being used, the Windows Narrator (sometimes called a "screen reader") reads the <title> tag in the page that opens in the task pane. When Internet Explorer 11 is being used, the Narrator reads the title bar of the task pane, which comes from the <DisplayName> value in the add-in's manifest.

2 See the update history page and how to find your Office client version and update channel for more details.

3 If your add-in includes the <Runtimes> element in the manifest, then it will not use Microsoft Edge with the original WebView (EdgeHTML). If the conditions for using Microsoft Edge with WebView2 (Chromium-based) are met, then the add-in uses that browser. Otherwise, it uses Internet Explorer 11 regardless of the Windows or Microsoft 365 version. For more information, see Runtimes.

4 On Windows versions prior to Windows 11, the WebView2 control must be installed so that Office can embed it. It's installed with Microsoft 365, version 2101 or later, and with one-time purchase Office 2021 or later; but it isn't automatically installed with Microsoft Edge. If you have an earlier version of Microsoft 365 or one-time purchase Office, use the instructions for installing the control at Microsoft Edge WebView2 / Embed web content ... with Microsoft Edge WebView2. On Microsoft 365 builds before 16.0.14326.xxxxx, you must also create the registry key HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\WEF\Win32WebView2 and set its value to dword:00000001.


Internet Explorer 11 does not support JavaScript versions later than ES5. If any of your add-in's users have platforms that use Internet Explorer 11, then to use the syntax and features of ECMAScript 2015 or later, you have two options.

  • Write your code in ECMAScript 2015 (also called ES6) or later JavaScript, or in TypeScript, and then compile your code to ES5 JavaScript using a compiler such as babel or tsc.
  • Write in ECMAScript 2015 or later JavaScript, but also load a polyfill library such as core-js that enables IE to run your code.

For more information about these options, see Support Internet Explorer 11.

Also, Internet Explorer 11 does not support some HTML5 features such as media, recording, and location. To learn more, see Determine at runtime if the add-in is running in Internet Explorer.

Troubleshooting Microsoft Edge issues

Service Workers are not working

Office Add-ins do not support Service Workers when the original Microsoft Edge WebView, EdgeHTML, is used. They are supported with the Chromium-based Edge WebView2.

Scroll bar does not appear in task pane

By default, scroll bars in Microsoft Edge are hidden until hovered over. To ensure that the scroll bar is always visible, the CSS styling that applies to the <body> element of the pages in the task pane should include the -ms-overflow-style property and it should be set to scrollbar.

When debugging with the Microsoft Edge DevTools, the add-in crashes or reloads

Setting breakpoints in the Microsoft Edge DevTools can cause Office to think that the add-in is hung. It will automatically reload the add-in when this happens. To prevent this, add the following Registry key and value to the development computer: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Wef]"AlertInterval"=dword:00000000.

When the add-in tries to open, get "ADD-IN ERROR We can't open this add-in from the localhost" error

One known cause is that Microsoft Edge requires that localhost be given a loopback exemption on the development computer. Follow the instructions at Cannot open add-in from localhost.

Get errors trying to download a PDF file

Directly downloading blobs as PDF files in an add-in is not supported when Edge is the browser. The workaround is to create a simple web application that downloads blobs as PDF files. In your add-in, call the Office.context.ui.openBrowserWindow(url) method and pass the URL of the web application. This will open the web application in a browser window outside of Office.

See also