| dm2 | Toad Data Modeler 2 Data |
| dmb | BYOND Dream Maker Compiled World |
| dmd | Domain Model Definition |
| dmd | SQL Developer Data Modeler Design |
| dmdl | Asakusa Framework DMDL Model Data |
| dmdz | SQL Developer Data Modeler Design |
| dml | PowerDynamo Dynascript Script |
| dmm | BYOND Dream Maker Map |
| dmt | Delphi Menu Template |
| dmx | Microsoft SQL Server Data Mining Extension |
| dni | IAR System Debugger Initialization Data |
| dnx | IBM Rational Software Architect DNX Diagram |
| do | Stata Batch File |
| dob | Visual Basic ActiveX Document Form |
| docbook | DocBook Document |
| docset | Doxygen Document Set File |
| docstates | Visual Studio Document Tab State Data |
| dof | Delphi Option File |
| doh | Geoworks GEOS Dependency Information |
| dol | Uniface Global Object Data |
| dotfuproj | Microsoft Visual Studio Dotfuscator Project |
| dox | Visual Basic ActiveX Document Binary Form |
| doxy | Doxygen Data |
| dpb | ProWorx NXT Descriptor Pointer with Blocking |
| dpd | ABC Dyadic Predicate Data |
| dpf | ProWorx NXT Descfriptor Pointer File |
| dpk | Delphi Package |
| dpkw | Delphi Package for Windows |
| dpl | Delphi Package Library |
| dplt | AppleScript Droplet |
