File with a .MDE extension contains an add-on to Microsoft Access application, in a binary form. Due to compressed form of the add-on, it is secured from unauthorised changes.

MDE files are created as a result of compiling Visual Basic for Application – VBA – source code, stored in a file with the MDA extension. The MDE add-ons in MS Access are used to expand the functionality of the application, in order to enable managing relational databases.