Copilot in Word With Word for the Web: Add-In Compatibility Reference

You use Copilot in Word to draft, rewrite, and summarize documents. When you switch to Word for the Web, some add-ins may stop working or behave differently. This article lists which add-in types are compatible when Copilot is active in Word for the Web. It also explains the technical reasons behind compatibility limits and offers configuration steps for administrators.

Add-ins extend Word functionality through task panes, content controls, and custom ribbons. Copilot in Word for the Web runs on a sandboxed platform that restricts certain add-in capabilities. Understanding these restrictions helps you plan your document workflows and avoid unexpected errors.

This reference covers add-in categories, version requirements, and known limitations. It also includes a comparison table for quick decision-making and troubleshooting tips for common failures.

Why Add-In Compatibility Differs Between Desktop and Web

Copilot in Word for the Web runs in a browser-based environment that enforces strict security boundaries. The Web platform uses a sandboxed JavaScript runtime that limits direct access to the document object model. Add-ins that rely on the Office.js library version 1.2 or earlier cannot communicate with Copilot because Copilot uses a newer API surface for real-time collaboration.

Sandbox Restrictions

Word for the Web isolates each add-in in its own iframe. Copilot operates in a separate iframe with elevated privileges for AI processing. When an add-in tries to read or write the document while Copilot is running a generation task, the platform queues the request and returns an error if the timeout exceeds 500 milliseconds. This affects add-ins that perform continuous spell-check, grammar suggestions, or auto-saving functions.

API Version Requirements

Add-ins must target Office.js version 1.3 or higher to register event handlers that coexist with Copilot. Add-ins built on version 1.1 or 1.2 cannot subscribe to the Document.ActiveViewChanged event, which Copilot uses to pause its own operations. As a result, these older add-ins may cause Copilot to freeze or produce partial output.

Steps to Verify and Configure Add-In Compatibility

Follow these steps to check whether an add-in will work when Copilot is active in Word for the Web. Perform these actions in the Microsoft 365 admin center or directly in the browser.

1. Open the add-in manifest file
   Locate the XML manifest file for the add-in. The file is usually named manifest.xml and is uploaded to the Microsoft 365 admin center or distributed through AppSource.
2. Check the schema version
   Look for the xmlns attribute in the root OfficeApp element. The value must be http://schemas.microsoft.com/office/appforoffice/1.1 or later. If the version is 1.0, the add-in is not compatible.
3. Verify the permissions level
   In the manifest, find the Permissions element. The value must be ReadWriteDocument or ReadAllDocument. Add-ins with Restricted permissions cannot interact with Copilot.
4. Test in Word for the Web with Copilot off
   Open a document in Word for the Web. Disable Copilot by clicking the Copilot icon on the ribbon and selecting Disable. Insert the add-in from the Insert > Add-ins menu. If the add-in loads without errors, proceed to the next step.
5. Enable Copilot and run a command
   Re-enable Copilot. Type a prompt such as Summarize this document. Wait for the output. If the add-in continues to function, it is compatible. If the add-in pane shows a loading spinner or an error message, the add-in is not compatible.

If Copilot and an Add-In Conflict in Word for the Web

Copilot generates content but the add-in pane displays a blank screen

This occurs when the add-in uses the Office.context.document.getFileAsync method to retrieve the document. Copilot locks the document stream during generation. The add-in must wait for Copilot to finish. To fix this, either disable the add-in while using Copilot or update the add-in to use the Office.context.document.getSelectedDataAsync method instead.

Add-in buttons on the ribbon are grayed out after Copilot runs

Copilot temporarily elevates its own ribbon priority. Add-ins that do not declare a RibbonTab element in the manifest lose their active state. Check the add-in manifest for a RibbonTab element with a StartupBehavior attribute set to Load. If the element is missing, contact the add-in vendor for an update.

Copilot returns generic output instead of tenant-specific data

Some add-ins modify the document metadata or headers. Copilot reads the document context from the file properties. If an add-in alters the Subject or Tags fields, Copilot may lose grounding. Remove the add-in, save the document, and then run Copilot again. If the problem resolves, the add-in is interfering with document properties.

Copilot in Word for the Web vs Desktop: Add-In Compatibility Differences

Item	Word for the Web with Copilot	Word Desktop with Copilot
Add-in manifest schema	v1.1 or later required	v1.0 or later supported
Task pane add-ins	Read-only during Copilot generation	Full read/write access
Content add-ins	Blocked when Copilot is active	Allowed with queued operations
Mail add-ins	Not supported	Not supported
Custom ribbon tabs	Disabled during Copilot commands	Enabled throughout
Office.js version minimum	1.3	1.1
Event handlers supported	Document.ActiveViewChanged only	All document events

You can now identify which add-ins work with Copilot in Word for the Web and which do not. Check each add-in manifest against the schema and permissions requirements listed above. For add-ins that fail the compatibility test, ask the vendor for an update that targets Office.js version 1.3 or later. As an advanced step, use the Microsoft 365 admin center to deploy add-ins with a targeted release policy so you can test new versions before rolling them out to all users.