.MXD File Extension
File TypeArcGIS Map Document
File format categories include Binary, Text, XML, and Zip. The format of this file type has not been determined.
What is an MXD file?
Map file format used by ESRI mapping software, such as ArcMap; saved in a compound format that includes the map description, layout, and embedded objects saved in the map; organized into units called storages and streams.
NOTE: MXD map files may grow in size after being saved multiple times because they can become fragmented. Saving a fragmented map document as a new document may reduce its file size.