The New Outlook for Windows is built on a modern web platform, which changes how add-ins work. Traditional COM add-ins rely on deep system access that the new architecture does not support. This article explains which add-ins will migrate automatically and which ones require a new web add-in to function.
You will learn how to check your current add-ins and identify those that need replacement. We will also cover the steps to find and install a suitable web add-in alternative.
Key Takeaways: New Outlook Add-In Compatibility
- File > Get Add-ins: This store in New Outlook only contains approved web add-ins that are compatible with the new platform.
- Settings > General > Manage Add-ins: View all installed add-ins and see their status, including any that are disabled due to incompatibility.
- Web Add-In (Office Add-in): A modern add-in built with JavaScript and HTML that runs in a sandbox, required for New Outlook functionality.
Understanding Add-In Architecture in New Outlook
The classic Outlook desktop application uses Component Object Model add-ins. These COM add-ins are powerful because they can interact directly with Windows and the Outlook process. They can modify the user interface, read and write data to files, and automate complex tasks.
New Outlook is based on the same code as Outlook on the web. This shift to a web-based platform prioritizes security, performance, and cross-device consistency. The platform uses a different extension model called Office Add-ins, commonly referred to as web add-ins.
How Web Add-Ins Differ from COM Add-Ins
Web add-ins are built with standard web technologies like HTML, CSS, and JavaScript. They run inside a secure sandbox, separate from the core application. This design prevents them from directly accessing the file system or other applications on your computer. Their capabilities are defined by a set of permitted APIs provided by Microsoft.
This change means many specialized business add-ins for document management, CRM integration, or advanced email sorting that depend on COM will not work. They must be redeveloped as web add-ins by their publishers to function in the new client.
Checking Your Current Add-Ins and Their Status
Before switching, you can check which of your current add-ins are compatible. The process differs slightly between the classic and new applications.
In Classic Outlook for Windows
- Open the COM Add-ins dialog
Go to File > Options > Add-ins. At the bottom of the window, select COM Add-ins from the Manage dropdown and click Go. - Review the list
A dialog box shows all installed COM add-ins with checkboxes. Note the names of the add-ins you use regularly. This list shows what you have, not what will work in New Outlook.
In New Outlook for Windows
- Access your add-in settings
Click the Settings gear icon in the top-right corner. Go to General > Manage Add-ins. - Interpret the status
The My add-ins page shows everything installed. Add-ins that migrated successfully will be enabled. Incompatible COM add-ins may appear here but will be marked as disabled or show an error icon.
Finding and Installing Replacement Web Add-Ins
If a key add-in is incompatible, you need a web version. Start by checking with the add-in publisher for an updated version.
- Visit the official add-in store
In New Outlook, select File > Get Add-ins. This opens the integrated Office Store. - Search for your tool
Use the search bar to look for the add-in by name or its function, like PDF or CRM. Filter results by the Outlook category. - Add the new web add-in
Click on an add-in to see its details. Click the Add button to install it. You may need administrator approval if your organization manages add-ins centrally. - Pin the add-in to your ribbon
After installation, right-click the main ribbon and select Customize the Ribbon. Find the add-in under the Add-ins tab and add it to a custom group for easy access.
When a Web Add-In Replacement Is Not Available
My Business-Critical Add-In Has No Web Version
Contact the software vendor directly to inquire about their development roadmap for a New Outlook web add-in. Explain that COM add-in support is ending. If no plan exists, you may need to evaluate alternative products that offer similar functionality as a web add-in.
The New Web Add-In Lacks Key Features
Web add-in APIs are more limited than COM. A feature like silently printing attachments or auto-saving files to a specific network drive may not be possible. You must adapt your workflow or use a different desktop application alongside Outlook to perform that specific task.
Add-In Causes Performance Issues in New Outlook
Even compatible web add-ins can sometimes slow down the interface. If you experience lag, go to Settings > General > Manage Add-ins. Temporarily disable newer add-ins one by one to identify the culprit. Report performance issues to the add-in publisher.
COM Add-In vs Web Add-In: Core Differences
| Item | COM Add-In (Classic Outlook) | Web Add-In (New Outlook) |
|---|---|---|
| Development Technology | .NET, C++, VSTO | HTML, JavaScript, CSS |
| Installation & Deployment | MSI installer or manual DLL registration | Centralized Office Store or admin deployment |
| System Access | Full access to Windows APIs and file system | Restricted to Microsoft-provided JavaScript APIs |
| User Interface Integration | Can modify ribbons, menus, and task panes deeply | Adds buttons to ribbon and opens in a task pane or dialog box |
| Cross-Platform Support | Windows only | Windows, Mac, Web |
| Security Model | Runs with user’s permissions, higher risk | Runs in a sandbox, more secure by design |
You can now identify which of your Outlook add-ins will work in the new application. Use the Settings > Manage Add-ins page to check the status of each one. For missing functionality, search File > Get Add-ins for a modern replacement. A useful advanced tip is to use the Outlook on the web version in your browser to test web add-in compatibility before fully switching to the New Outlook desktop client.