| wut | WUTG Tag Data |
| wvd | StarMoney Filter Data |
| wvf | Yokogawa Waveform Data |
| wvm | Ricardo WAVE Input |
| wvs | Wanvas Data |
| wvt | IDGS101 Waveform Data |
| wwa | WebSite-Watcher Archive |
| wwb | Corel WordPerfect Button Bar Data |
| wwd | Microsoft Works Wizard Data |
| wwf | WAsP Wind Farm Data |
| wwg | CARE-S InfoWorks Wastewater Data |
| wwh | WAsP Workspace |
| wwi | WinWein Interchange Format Data |
| wwk | WAsP v7 Workspace |
| wwls | Weather Watcher Live Skin |
| wwq | SWAT Watershed Water Quality Input |
| wwr | WAsP v8 Resource Grid |
| wwtfig | WorldWide Telescope Constellation Figures Data |
| wwtl | WorldWide Telescope Layer Data |
| wwu | Wwise Work Unit |
| wxp | wxWidgets Package Description Data |
| wxw | Winradio Extended Wave Data |
| wxx | Worldographer Map Settings Data |
| wyc | wyUpdate Compressed Client Data |
| wys | wyBuild Server Data |
| wyu | wyBuild Update Data |
| wzd | Sharp Wizard Data |
| wzmul | WinZip Registration Data |
| wztheme | WinZip Theme Data |
| x00 | Paradox Secondary Index |
| x01 | Paradox Secondary Index |
| x02 | Paradox Secondary Index |
| x03 | Paradox Secondary Index |
| x04 | Paradox Secondary Index |
| x05 | Paradox Secondary Index |