| .D0 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .D15 | HERE | Uncommon Files | HERE Maps For Android Map Data Package | HERE Maps | HERE |
| .D82 | Commodore International | Uncommon Files | Commodore Emulator File | VICE | Open Source |
| .DA | Procedimientos-Uno, S.L. | Uncommon Files | DAwin Project File | DAwin | Procedimientos-Uno, S.L. |
| .DA! | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DA2 | Microsoft Corporation | Uncommon Files | Windows Dancer File | Windows Media Center | Microsoft Corporation |
| .DA5032 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DAEMONSCRIPT | Disc Soft Ltd. | Uncommon Files | Daemon Tools Script | DAEMON Tools | Disc Soft Ltd. |
| .DANGER | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DAP | SpeedBit | Uncommon Files | Download Accelerator Plus Partial Download | Download Accelerator Plus | SpeedBit |
| .DARBY | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DAT | Unknown Developer | Uncommon Files | Game Data | Dragon UnPACKer | Open Source |
| .DATALESS | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DATALINKHE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DATASOURCE | Microsoft Corporation | Uncommon Files | Microsoft Visual Studio Data Source | Microsoft Visual Studio | Microsoft Corporation |
| .DBX | Microsoft Corporation | Uncommon Files | Outlook Express E-mail Folder | Microsoft Outlook Express | Microsoft Corporation |
| .DC1 | DevCad | Uncommon Files | DevCad Document | DevCad Cam Pro | DevCad |
| .DCHB1 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DCTMP | Open Source | Uncommon Files | DC++ Partially Downloaded File | DC++ | Open Source |
| .DELTA | DigiSoft Innovations | Uncommon Files | An Unknown Apple II File | Golden Orchard | DigiSoft Innovations |
| .DESKTOP | Stardock Corporation | Uncommon Files | Desktop Entry File | Object Desktop | Stardock Corporation |
| .DFCOMPONEN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DFINE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DGC | Shin-ichi Tsuruta | Uncommon Files | DGCA File Archive | DGCA | Shin-ichi Tsuruta |
| .DICTIONARY | DigiSoft Innovations | Uncommon Files | An Unknown Apple II File | Golden Orchard | DigiSoft Innovations |
| .DIH | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DISPOSITIO | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DK | Unknown Developer | Uncommon Files | Danish Text/localization File | Unknown Software | Unknown Developer |
| .DLB | Symantec Corporation | Uncommon Files | Troj/Dloadr-AHT Data | Kaspersky Anti-Virus | Kaspersky Lab |
| .DLF | Belkin International | Uncommon Files | Belkin Router Firmware Update | Belkin Router Firmware Updater | Belkin International |
| .DLFA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DLM | AKAMAI | Uncommon Files | Akamai Download Manager File | Akamai Download Manager | AKAMAI |
| .DMJ | Unknown Developer | Uncommon Files | Dustman Selection for Delete File | Unknown Software | Unknown Developer |
| .DNA.XML | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DNAXML | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DOCUMENTAT | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DORE | Unknown Developer | Uncommon Files | Dore Raster Files Format | Unknown Software | Unknown Developer |
| .DOV | Safer Networking Ltd. | Uncommon Files | Temporary (Temp) File | FileAlyzer | Safer Networking Ltd. |
| .DOWNLOADING | Pando Networks | Uncommon Files | Pando Incomplete Download File | Pando | Pando Networks |
| .DOYO000 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DPB | Susteen, Inc. | Uncommon Files | DataPilot Backup File | DataPilot | Susteen, Inc. |
| .DR | Sony Mobile Communications | Uncommon Files | DRM Rights Object | DRM Packager | Sony Mobile Communications |
| .DR9 | Unknown Developer | Uncommon Files | Directory Files | Unknown Software | Unknown Developer |
| .DRAGONSFUN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DRC | Open Source | Uncommon Files | Open Mobile Alliance DRM Rights Object | Microsoft Notepad | Microsoft Corporation |
| .DRP | DÖRR EDV-Beratung | Uncommon Files | DReport Document | DReport | DÖRR EDV-Beratung |
| .DR_ | Unknown Developer | Uncommon Files | Compressed DRV File Of VFW | Unknown Software | Unknown Developer |
| .DSC | Kingsoft | Uncommon Files | Kingsoft Design Science Equation File | Kingsoft Office | Kingsoft |
| .DSJ | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DSSC | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DST- | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DSY | Lead System (M) Sdn. Bhd. | Uncommon Files | Besta Video File | Besta Electronic Dictionaries | Lead System (M) Sdn. Bhd. |
| .DTF | IBM | Uncommon Files | Domino Temporary File | IBM Domino | IBM |
| .DUPLICATEZ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DV | Roxio | Uncommon Files | Digital Video File | Microsoft Windows Live Movie Maker | Microsoft Corporation |
| .DVDREGIONC | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .DWC | Emulex Corporation | Uncommon Files | Emulex DWC Firmware Update File | Emulex lputil | Emulex Corporation |
| .DWEXPORTER | SolarWinds Inc. | Uncommon Files | DameWare Exporter File | DameWare Exporter | SolarWinds Inc. |
| .DWL | IMSI/Design, LLC | Uncommon Files | TurboCAD Drawing Lock File | TurboCAD | IMSI/Design, LLC |
| .DWN | Cambrionix | Uncommon Files | Firmware Update File | Cambrionix Firmware updater | Cambrionix |
| .DWR | Cedarville University | Uncommon Files | NetOp File | NetOp | Cedarville University |
| .DWV | Unknown Developer | Uncommon Files | WAV File | Unknown Software | Unknown Developer |
| .DXD | Dimensione CAD company | Uncommon Files | Diogenes Extended Document | Diogenes | Dimensione CAD company |
| .DXN | Fujitsu Limited | Uncommon Files | Fujitsu DexNET Fax Document File | dexNET | Fujitsu Limited |
| .DYA | DigiSoft Innovations | Uncommon Files | An Unknown Apple II File | Golden Orchard | DigiSoft Innovations |
| .D_T | Unknown Developer | Uncommon Files | Eru/erd File | Unknown Software | Unknown Developer |
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