| dmy | LTSTDB Time Series Data |
| dn | Adobe Dimension Model Data |
| dna | BioPerl DNA Sequence Data |
| dna | Desktop DNA Data Storage |
| dna | GenePool DNA Data |
| dna | SnapGene DNA Data |
| dnasym | Desktop DNA Compiled Application Script |
| dnax | Desktop DNA Exclusion List |
| dnb | Microsoft Windows Binary DNS Database |
| dnc | DANCE Database |
| dnd | ClustalW2 Guide Tree Data |
| dne | Netica ASCII Text Data |
| dnet | Netica ASCII Text Data |
| dnk | KillAd Data |
| dnl | Concordance Database |
| dnn | DotNetNuke Manifest Data |
| dnp | Neat Image Device Noise Profile |
| dns | Microsoft Windows DNS Server Database |
| dntu | DameWare NT Utilities Data |
| dnw | EMPOP DrawNetWork Data |
| do | Active-HDL DO Macro Data |
| do | Digital Line Graph Optional Vector Data |
| do | MicroSim PCBoard Autorouting Data |
| dock | DragThing Dock Data |
| dockerfile | Docker Settings Data |
| dockerignore | Docker Ignore File |
| dockpack | Stardock ObjectDock Package |
| docktheme | Stardock ObjectDock Theme |
| docmenx | Egis Encrypted DOCM Data |
| docmeta | Bukkit Information Data |
