Opening MSO files

Have a problem opening a .MSO file? We collect information about file formats and can explain what MSO files are. Additionally we recommend software suitable for opening or converting such files.

What is the .MSO file type?

The .mso filename extension represents the Microsoft Office Embedded OLE Object Storage (.mso) file type, with reference to the proprietary binary format developed by Microsoft Corporation for embedding Microsoft Office documents. The .mso file type has become known because of the "oledata.mso" file, often received as an e-mail message attachment. The "oledata.mso" file is a gzip-compressed binary storage for embedded OLE (Object Linking and Embedding) objects, used as a wrapper for Microsoft Office documents sent by e-mail using Microsoft Office Outlook in the HTML mode (default) and supposed to be handled transparently on the receiver's side. On non-Windows systems or if Microsoft Office Outlook is not used as the e-mail client, the "oledata.mso" file is shown to the user in the attachment, possibly in combination with additional .png, .emz, or .wmz files. The MSO file format has not been documented by Microsoft, and such files are not meant to be directly opened by the user. The original attachment may be accessed by opening the e-mail message in Microsoft Outlook (Microsoft Entourage).

Software to open or convert MSO files

You can open MSO files with the following programs: 

Popular formats