| 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 User 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 |
| dpc | Delphi Package Collection |
| 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 |
| dpmi | DOS Protected-Mode Interface Data |
| dpo | Delphi Object Repository |
| drc | Delphi Resource Strings |
| dres | Delphi Compiled Resource |
| dro | Delphi Repository Object |
| ds | DAZ Studio ASCII Script |
| dsa | DAZ Studio ASCII Script |
| dsb | DAZ Studio Binary Script |
