| ddd | Verity Server Data |
| dde | ABBYY Lingvo Dictionary Error Log |
| ddg | Deltadrive GRS Database |
| ddg | DucatiDiag Data File |
| ddg | MAP GMS Installation Document |
| ddi | MAP IEC Document |
| ddl | Ovation Pro DDL |
| ddoc | DigiDoc Digital Signature |
| ddp | Dinkey Dongle Parameter File |
| ddr | DDRemote Saved Parameters |
| ddr | MAP Parameterisation Document |
| ddrt | LeCroy DDR Trace Data |
| dds | MAP Service Document |
| ddt | Oracle Documaker GenData Dataprocessing Rules Data |
| ddu | MAP dlms User Association Document |
| ddwscan | Disk Drill Scan Data |
| ddy | ASHRAE Design Conditions Design Day Data |
| de2 | eXtendable Wad Editor DE2 Data |
| dea | Drug Enforcement Administration Data |
| debuglog | MyDefrag Debug Log |
| dee | Creator Circuit Description File |
| deejam | GSpot Codec Data |
| def | SmartWare Definition Data |
| deform | FontTwister Deform Guide Line Data |
| defxml | Danea Easyfatt Data |
| dei | Gerber Design Engineered Interface Data |
| dek | Memorize-It Deck File |
| del | Lucene Deleted Documents Data |
| delta | Firebird SQL Delta Data |
| dem | SOBEK Digital Elevation Map Data |