| .WBS | Tech4Learning | Ficheiros Web | WebBlender Project File | WebBlender 2 | Tech4Learning |
| .WDGT | Opera Software | Ficheiros Web | Opera Widget File | Opera | Opera Software |
| .WEB | Magix Software GmbH | Ficheiros Web | Xara Web Document | MAGIX Xara Web Designer 11 | Magix Software GmbH |
| .WEBARCHIVE | Apple | Ficheiros Web | Safari Web Archive | Apple TextEdit | Apple |
| .WEBARCHIVE FILE EXTENSION | Apple | Ficheiros Web | Apple Safari Web Archive | Safari | Apple |
| .WEBLOC | Apple | Ficheiros Web | Mac OS X Website Location | Microsoft Notepad | Microsoft Corporation |
| .WEBSITE | Microsoft Corporation | Ficheiros Web | Internet Explorer Pinned Site Shortcut | Internet Explorer | Microsoft Corporation |
| .WGP | WebHat Software | Ficheiros Web | Web Gallery Project | Web Gallery Software | WebHat Software |
| .WGT | Interscape | Ficheiros Web | IMPS Data File | CSPro | Interscape |
| .WHTT | Open Source | Ficheiros Web | HTTrack Website Copier File | HTTrack | Open Source |
| .WIDGET | Microsoft Corporation | Ficheiros Web | Microsoft Windows Mobile Widget | Microsoft Visual Studio | Microsoft Corporation |
| .WML | Syncro Soft | Ficheiros Web | Wireless Markup Language File | Internet Explorer | Microsoft Corporation |
| .WN | WN | Ficheiros Web | WN Web File | WN | Open Source |
| .WOA | Apple | Ficheiros Web | WebObjects Application | Internet Explorer | Microsoft Corporation |
| .WPP | Serif | Ficheiros Web | WebPlus Project File | Serif WebPlus | Serif |
| .WPX | Microsoft Corporation | Ficheiros Web | Printer Description File 2 | Microsoft Windows | Microsoft Corporation |
| .WRF | Cisco Systems | Ficheiros Web | WebEx Recording | Cisco WebEx Player | Cisco Systems |
| .WSDL | Microsoft Corporation | Ficheiros Web | Web Services Description Language File | Microsoft Visual Studio | Microsoft Corporation |
| .WSIM | Open Source | Ficheiros Web | FirstStop WebSearch Import Module | FirstStop WebSearch | Open Source |
| .XBEL | Python Software Foundation | Ficheiros Web | XBEL Bookmarks File | Arora | Open Source |
| .XBL | Open Source | Ficheiros Web | XBLite Source Code File | XBLite | Open Source |
| .XFDL | IBM | Ficheiros Web | Extensible Forms Description Language | Microsoft Notepad | Microsoft Corporation |
| .XHR | Microsoft Corporation | Ficheiros Web | XMLHttpRequest | Google Chrome | Google |
| .XHT | Open Source | Ficheiros Web | XHTML File | Google Chrome | Google |
| .XHTM | Opera Software | Ficheiros Web | Extensible Hypertext Markup Language Document | Internet Explorer | Microsoft Corporation |
| .XHTML | Opera Software | Ficheiros Web | Extensible Hypertext Markup Language Document | Internet Explorer | Microsoft Corporation |
| .XSS | Oracle Corporation | Ficheiros Web | XML Style Sheet | Microsoft Visual Studio | Microsoft Corporation |
| .XTML | Altairis | Ficheiros Web | XML4web Virtual HTML Document | XML4web | Altairis |
| .XUL | Mozilla | Ficheiros Web | XML User Interface Language File | Netscape Navigator | NetScape |
| .XWS | Magix Software GmbH | Ficheiros Web | Xara Web Designer Graphic | Xara Designer Pro X | Magix Software GmbH |
| .ZFO | Software602 | Ficheiros Web | XSL-FO Online Form | Software602 602XML Form Filler | Software602 |
| .ZPWEB | Zeta Producer | Ficheiros Web | Zeta Producer Web Document | Zeta Producer | Zeta Producer |
| .ZVZ | Unknown Developer | Ficheiros Web | Possible Virus File | Should Not Be Opened Manually | Unknown Developer |
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