| ddcx | DivX Descriptor 2 |
| ddd | Digital Tachograph Data |
| ddd | Verity Server Data |
| dde | ABBYY Lingvo Dictionary Error Log |
| ddg | MAP GMS Installation Document |
| ddg | DucatiDiag Data File |
| ddg | Deltadrive GRS Database |
| ddi | MAP IEC Document |
| ddl | Ovation Pro DDL |
| ddoc | DigiDoc Digital Signature |
| ddp | Dinkey Dongle Parameter File |
| ddr | MAP Parameterisation Document |
| ddr | DDRemote Saved Parameters |
| dds | MAP Service Document |
| ddu | MAP dlms User Association Document |
| ddy | ASHRAE Design Conditions Design Day Data |
| dea | Drug Enforcement Administration Data |
| dee | Creator Circuit Description File |
| dek | Memorize-It Deck File |
| del | Lucene Deleted Documents Data |
| den | XMVB Density Data |
| deploy | ClickOnce Deployment Data |
| dess | Microsoft Device Emulator Saved State Data |
| det | Act! Email Message |
| deu | Adobe Acrobat Reader German Language Data |
| devx | E-Sword Devotional Data |
| dez | DataEase v4 Data File |
| df | Lightscape Parameter File |
| df | Paradox Table Filter |
| df7 | Omnis Studio v7 Database |
