| .DB | Dwayne Richard Hipp | Databasefiler | Mobile Device Database File | Apache OpenOffice | Apache Software Foundation |
| .DBF | dBase, LLC | Databasefiler | Database File | Apache OpenOffice | Apache Software Foundation |
| .DIF | Microsoft Corporation | Datafiler | Data Interchange Format | Apache OpenOffice | Apache Software Foundation |
| .DIZ | Unknown Developer | Tektfiles | Description In Zip File | OpenOffice Writer | Apache Software Foundation |
| .DO | Unknown Developer | Web-Filer | Java Servlet | Apache Tomcat | Apache Software Foundation |
| .DOC | Microsoft Corporation | Tektfiles | Microsoft Word Document (before The 2007 Version) | Apache OpenOffice | Apache Software Foundation |
| .DOCM | Microsoft Corporation | Tektfiles | Word Open XML Macro-Enabled Document | Apache OpenOffice | Apache Software Foundation |
| .DOCX | Microsoft Corporation | Tektfiles | Microsoft Word Open XML Document | OpenOffice Writer | Apache Software Foundation |
| .DON | Apache Software Foundation | Datafiler | Apache OpenOffice (OpenOffice.org) Log | Apache OpenOffice | Apache Software Foundation |
| .DOT | Microsoft Corporation | Sideutformingsfiler | Word Document Template | Apache OpenOffice | Apache Software Foundation |
| .DOTM | Microsoft Corporation | Sideutformingsfiler | Word 2007 XML Macro-Enabled Template | Apache OpenOffice | Apache Software Foundation |
| .DOTX | Microsoft Corporation | Sideutformingsfiler | Word 2007 XML Template | Apache OpenOffice | Apache Software Foundation |
| .DPC | Microsoft Corporation | Datafiler | Microsoft Office Resource File | Apache OpenOffice | Apache Software Foundation |
| .DUMP | Microsoft Corporation | Systemfiler | Dump File | Apache OpenOffice | Apache Software Foundation |
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