.MDI File Extension

High-resolution, tag-based graphics format developed from the TIFF format; used by Microsoft Office for saving scanned documents; may be turned into a Word (.DOC) document using OCR (optical character recognition) software.

MDI files are created and opened with Microsoft Office Document Imaging (MODI), which is included with Office XP, 2003, and 2007. Microsoft stopped including MODI with Office 2010, so you can't open MDI files in Office 2010.

NOTE: Saving documents created with Office Document Imaging in the .TIF format allows for better compatibility with other programs.