| .W | Progress Software Corporation | Uncommon Files | OpenEdge Architect Source Code File | OpenEdge | Progress Software Corporation |
| .W2F | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .W73 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WAL | Nullsoft | Uncommon Files | Winamp Modern Skin | Nullsoft Winamp | Nullsoft |
| .WBA | Stardock Corporation | Uncommon Files | WindowBlinds Compressed Skin | WindowBlinds | Stardock Corporation |
| .WC4 | Unknown Developer | Uncommon Files | WinCheckIt4 Settings File | Unknown Software | Unknown Developer |
| .WCINV | Microsoft Corporation | Uncommon Files | Windows Meeting Space Invitation File | Windows Meeting Space | Microsoft Corporation |
| .WCM | Corel | Uncommon Files | WordPerfect Macro | Corel WordPerfect X8 | Corel |
| .WCXF | PenPower | Uncommon Files | WorldCard Exchange File | WorldCard Mobile | PenPower |
| .WDSEML | Mozilla | Uncommon Files | Thunderbird Searchable Email File | Mozilla Thunderbird | Mozilla |
| .WEBARCHIV | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WEI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .WER | Microsoft Corporation | Uncommon Files | Windows Error Report File | Microsoft Notepad | Microsoft Corporation |
| .WF2 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .WGS | ChannelAdvisor | Uncommon Files | Walk-Graph Segment File | RichFX Player | eHelp Corporation |
| .WINDOWSLIV | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .WINDOWSMED | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WJE | Mariner Software | Uncommon Files | WinJournal Entry | WinJournal | Mariner Software |
| .WKO | Applied Training Science | Uncommon Files | Workout Template File | RippedPro | Applied Training Science |
| .WKSP | Tethys Solutions | Uncommon Files | Workspace Macro Pro File | Workspace Macro Pro | Tethys Solutions |
| .WM5 | Unknown Developer | Uncommon Files | Dyndlg2 File | Dyndlg2 | Unknown Developer |
| .WMH | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WNK | Satish Kumar | Uncommon Files | Wink Presentation | Wink | Satish Kumar |
| .WNS | Broderbund | Uncommon Files | PrintShop Newsletter File | PrintShop | Broderbund |
| .WPJ | Watcom International Corporation | Uncommon Files | Watcom C/C++ Project | Watcom C/C++ | Open Source |
| .WPU | Archaeopteryx Software, Inc. | Uncommon Files | User-specific Project File | Wing IDE | Archaeopteryx Software, Inc. |
| .WRX | Progress Software Corporation | Uncommon Files | Progress File | Progress | Progress Software Corporation |
| .WS1 | Microsoft Corporation | Uncommon Files | WordStar For Windows 1 File | Microsoft Wordstar | Microsoft Corporation |
| .WSQ | UTAU Team | Uncommon Files | UTAU File | UTAU | Vocal Synthesizer |
| .WSZ | Nullsoft | Uncommon Files | Winamp Classic Skin | Nullsoft Winamp | Nullsoft |
| .WT | WildTangent | Uncommon Files | Branded .X 3D Model File | WildTangent FATE | WildTangent |
| .WTC | Logitech | Uncommon Files | Logitech Webcam File | Logitech Webcam Software | Logitech |
| .WTK | Interscape | Uncommon Files | WinTalk URL Address | WinTalk | Interscape |
| .WTP | Satish Kumar | Uncommon Files | Wink Template | Wink | Satish Kumar |
| .WUL | Open Source | Uncommon Files | WinUHA Language File | WinUHA | Open Source |
| .WWD | Microsoft Corporation | Uncommon Files | Works Wizard File | Microsoft Works | Microsoft Corporation |
| .WWK | Corel Corporation | Uncommon Files | Corel WordPerfect Keyboard Layout File | Corel WordPerfect | Corel |
| .WWM | Dalin-Service | Uncommon Files | WeeWheel File | WeeWheel | Dalin-Service |
| .WWZ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WXB | Microsoft Corporation | Uncommon Files | Windows Miscellaneous File | Microsoft Windows | Microsoft Corporation |
| .WXM | Open Source | Uncommon Files | wxMaxima Batch File | wxMaxima | Open Source |
| .WXW | WiNRADiO | Uncommon Files | WiNRADiO Extended Wave File | Unknown Software | Unknown Developer |
| .WYG | CAST Group of Companies Inc. | Uncommon Files | WYSIWYG File | Cast Soft wysiwyg | CAST Software |
| .WYN | Freedom Scientific | Uncommon Files | WYNN Document File | WYNN | Freedom Scientific |
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