In the Word desktop application, remove the unsupported features. In Word for the web, click Open in Word (requires Word 2003, or later, or Word for Mac 2008 12.2.9 or later). If someone in the group doesn’t have one of those versions of Word, you need to remove the unsupported features from the document so that everyone can continue to work together in Word for the web. If everyone in the group has Word 2010, Word 2013, or Word for Mac 2011, continue working together in Word (click Open in Word and continue editing). If someone does save the document with features that aren’t supported by Word for the web, you can still co-author, just not in Word for the web anymore. If you want to restrict access to the document, use the permission features where the document is stored (OneDrive, Microsoft 365, or SharePoint). For example, don’t use permission features such as editing restrictions or marking the document as final. In the Word desktop application, be careful not to introduce content or functionality to the document that will prevent other authors from editing the document in Word for the web. Note: Co-authoring in the Word desktop application requires Word 2010, Word 2013, or Microsoft Word for Mac 2011.
