Troubleshoot co-authoring Word documents

Word for the web and desktop versions Word provide the ability for more than one person to edit a document at the same time (co-authoring). If you can't co-author a document, one or more of the following reasons might be the cause:

• The document is open in a version of the Word desktop application that doesn't support co-authoring. 

• The document is stored on a server that does not support co-authoring. Co‑authoring works with OneDrive or SharePoint Online.

• The file format is not supported. Only .docx documents can be co-authored in Word for the web. When you click Edit in Browser, Word for the web prompts you to convert a .doc file to the new format. Click Convert, and then click Edit. Be sure your co-authors work with the .docx document. You might want to append "backup" to the file name of the original document, which Word for the web stores in the same folder as the .docx copy it creates.

• The document is marked as final to prevent accidental changes. If you need to edit the document, open it in Word and turn off Mark as Final.

• The document contains an OLE object, or the body of the document contains an ActiveX control.

• The document does not have the Store random numbers to improve Combine accuracy check box selected. (On the ribbon, click the File tab, click Options to display the Word Options dialog box, click Trust Center, click Trust Center Settings to display the Trust Center dialog box, click Privacy Options, and then under the Document-specific settings section, make sure the Store random numbers to improve Combine accuracy check box is selected.)

• The document is a very large file size. For tips on reducing the file size of documents see Reduce the file size of a picture.

• Certain Microsoft Office group policy settings prevent co-authoring, including Disable Automerge Client Policy and Disable Co-Authoring Client Policy.

• The document is checked out, password‑protected, or encrypted using Information Rights Management (IRM) or sensitivity labels that do not support co‑authoring.

• The document uses master documents with subdocuments or contains HTML frame sets.