| dill | Dart Compiled Binary |
| din | DataEase Installation Script |
| disco | Visual Studio .NET Discovery Data |
| dj | DJGPP Source Code |
| dj2 | DJGPP Source Code |
| djg | DJGPP Makefile |
| dl3 | VS10XX VSOS Application |
| dlct | AppleScript Dialect Data |
| dldi | libfat Dynamically Linked Device Interface |
| dlg | Visual C++ Dialog |
| dlk | Transputer Development System Occam Compiler Link Info |
| dm | BYOND Dream Maker Source Code |
| dm1 | ER/Studio Data Model |
| dm2 | Toad Data Modeler 2 Data |
| dmb | BYOND Dream Maker Compiled World |
| dmd | SQL Developer Data Modeler Design |
| dmd | Domain Model Definition |
| 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 |
| 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 |
| dof | Delphi Option File |
| doh | Geoworks GEOS Dependency Information |
| 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 |