File with a .DIM extension contains a message stored in a binary format, which holds one or many types of files or data; used to transfer data across Internet. Such file contains information on length, type and identifier of each type of data contained within it.

DIM messages were used in the Web servers and emails. They change a binary file into a data package possible to read for a user. This format was developed in the year 2001 by Microsoft, as an upgrade of MIME, however, it did not enter general use and did not acquire the RFC statute.