Develop Outlook add-ins for the new Outlook on Windows (preview)
The new Outlook on Windows desktop client unifies the Windows and web codebases to create a more consistent Outlook experience for users and administrators. Its modern and simplified interface has added capabilities and aims to improve productivity, organization, and collaboration for users. More importantly, the new Outlook on Windows supports Outlook web add-ins, so that you can continue to extend Outlook's functionality.
Impact on VSTO and COM add-ins
The new Outlook on Windows aims to unify the extensibility experience across all Outlook platforms. To provide a more reliable and stable add-in experience, VSTO and COM add-ins aren't supported in the new Outlook on Windows. To ensure your add-in continues to work in the new Outlook on Windows, you must migrate your VSTO or COM add-in to an Outlook web add-in. Migrating to an Outlook web add-in not only enables compatibility with the new Outlook on Windows, it also makes your solution available to users on other platforms, such as Outlook on Mac, on mobile, or on the web.
To help get you started on the migration process, review the following guidance.
- The differences in features and scenarios supported by VSTO and COM add-ins and Outlook web add-ins are being addressed. To determine whether your add-in scenario is fully supported in an Outlook web add-in, see Supported scenarios in Outlook web add-ins.
- For guidance on how to transition your VSTO add-in to an Outlook web add-in, see VSTO add-in developer's guide and Tutorial: Share code between both a VSTO Add-in and an Office Add-in with a shared code library.
- If you're new to Outlook web add-ins, try out the Outlook quick start to build your first add-in.
- If you're an IT administrator and would like to learn more about how to transition to Outlook web add-ins in your organization, see Transitioning add-ins from classic Outlook to the new Outlook for Windows.
VSTO and COM add-ins are still supported in classic Outlook on Windows.
Supported scenarios in Outlook web add-ins
The following table identifies key Outlook scenarios and their support status in a web add-in. This table will be updated as additional scenarios are supported. Periodically check this section as you plan to migrate your VSTO or COM add-in.
As we continue to update the table of supported scenarios, if you want to view the recent changes made, select Edit This Document (pencil icon) from the top right corner of the article, then select History.
To learn more about Outlook add-in features that are in preview, see Outlook add-in API preview requirement set.
There are various possibilities for extending the Outlook functionality through add-ins. If your VSTO or COM add-in solution doesn't quite fit any of the scenarios in the table, complete the survey to share your scenario.
Support for classic Outlook on Windows
The classic Outlook on Windows desktop client will continue to support the development of new and existing Outlook web add-ins. Additionally, it will continue to receive releases of the latest Outlook add-in features.
Test your add-in in the new Outlook on Windows
Test your Outlook web add-in in the new Outlook on Windows today! To switch to the new Outlook on Windows that's in preview, you must meet the following requirements.
Have a Microsoft 365 work or school account connected to Exchange Online. The new client doesn't currently support on-premises, hybrid, or sovereign Exchange accounts.
Have a minimum OS installation of Windows 10 Version 1809 (Build 17763).
Be a member of the Microsoft 365 Insider program.
To help you sign up and install the Outlook desktop client, see Getting started with the new Outlook for Windows.
For guidance on how to sideload your add-in, see Sideload Outlook add-ins for testing.
Debug your add-in
To debug an add-in installed in the new Outlook on Windows desktop client, first sideload the add-in to Outlook on the web. Then, follow the guidance in Debug add-ins in Office on the web to use your browser's developer tools for debugging.
Development experience feedback
As you test your Outlook web add-in in the new Outlook on Windows, share feedback on your experience with the developer community through GitHub.
- Blog post: New Outlook for Windows available to all Office Insiders
- Blog post: Add-ins in the new Outlook for Windows
- Podcast: Update on development with new Outlook for Windows
- Outlook add-ins overview
- Build your first Outlook add-in
- VSTO add-in developer's guide
- Tutorial: Share code between both a VSTO Add-in and an Office Add-in with a shared code library