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Compound File Binary File Format

Compound File Binary File Format or CFBF is an older binary file format developed by Microsoft for use in the earlier versions of Microsoft Office applications. This format was used exclusively until Microsoft Office 2007, when Microsoft introduced a newer Office Open XML file format. CFBF is still supported in all Microsoft Office applications for backward compatibility and Microsoft Outlook (.msg), Microsoft Visio (.vsd) and Microsoft Publisher (.pub) still use CFBF as a primary file format for their files. And even for Microsoft Office applications with a newer Open Office XML file format there are many files which are stored in older CFBF file format which need to be converted. File extensions which are based on CFBF include: .doc, xls, .ppt, .msg, .vsd, .pub.

If you need to open a CFBF based file you need to either get a corresponding Microsoft Office application and open it there or use an offline or online converter to convert it to a different file format which you can use. Besides that, you can upload your older Microsoft Office file into Microsoft Office Online or Google Docs and open them from there. Both of these online office packages have conversion from older CFBF based files.

Microsoft CFBF file format used to be completely proprietary until 2010 when Microsoft released a spec for Compound File Binary File Format to the public. Now it is possible for 3rd party developers to parse this format and create tools based on it. If you need to look into internals of CFBF file you can download OffVis 1.0 Beta tool. This tool can open CFBF files and display their content in a tree like structure with details like data types and offsets in a binary data displayed. You can even view raw binary data for specific structure if you need to.

Great introduction to CFBF file format is available at Microsoft Open Specifications Support Team Blog. You can also read a full specification at [MS-CFB]: Compound File Binary File Format page.

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  Rights-Managed Email Object Protocol File
Opens with
  Microsoft Outlook
  Microsoft Outlook Web App (OWA)
  Azure Information Protection viewer