| .WEAP | id Software | Fişiere de jocuri | Quake 3 Engine Weapon File | AbiWord | Open Source |
| .WEBARCHIVE | Apple | Fișiere web | Safari Web Archive | WebArchive Extractor | Open Source |
| .WEBM | Google | Fişiere video | WebM Video File | Eltima Elmedia Player | Open Source |
| .WEBP | Google | Fişiere de imagini rastru | Google Image File Format | IrfanView | Open Source |
| .WGM | Open Source | Fişiere de jocuri | Chalk Game Data | Chalk | Open Source |
| .WGT | Interscape | Fişiere de date | IMPS Data File | Xwindow Neuro Bio Clusters | Open Source |
| .WHTT | Open Source | Fișiere web | HTTrack Website Copier File | HTTrack | Open Source |
| .WI | Open Source | Fişiere de imagini rastru | Wavelet Image | DjVu Reader | Open Source |
| .WIM | Microsoft Corporation | Fişiere de imagini de disc | Windows Imaging Format File | ExtractNow | Open Source |
| .WINGS | Open Source | Fişiere de imagini 3D | Wings 3D File | Wings 3D | Open Source |
| .WK! | IBM | Fişiere foi de calcul | Lotus 1-2-3 Spreadsheet | Gnumeric | Open Source |
| .WK1 | IBM | Fişiere de date | Lotus Worksheet | Gnumeric | Open Source |
| .WK4 | IBM | Fişiere de date | Lotus Lotus 1-2-3 V4 Worksheet | Gnumeric | Open Source |
| .WKB | Corel | Fişiere text | Corel WordPerfect Document | PostGIS | Open Source |
| .WMA | Microsoft Corporation | Fişiere audio | Windows Media Audio File | Eltima Elmedia Player | Open Source |
| .WML | Syncro Soft | Fișiere web | Wireless Markup Language File | AbiWord | Open Source |
| .WMV | Microsoft Corporation | Fişiere video | Windows Media Video File | Eltima Elmedia Player | Open Source |
| .WN | WN | Fișiere web | WN Web File | WN | Open Source |
| .WOFF | Open Source | Fişiere de caractere | Web Open Font Format File | FontForge | Open Source |
| .WOW | Open Source | Fişiere audio | Grave Composer Music Module | OpenMPT | Open Source |
| .WOWPROJ | Open Source | Fişiere de programator | AddOn Studio Project File | Addon Studio for World of Warcraft | Open Source |
| .WPB | PGN Inc. | Fişiere de imagini rastru | OpenCanvas 1.1 Image | Windows Phone Device Manager | Open Source |
| .WPJ | Watcom International Corporation | Fișiere neobișnuite | Watcom C/C++ Project | Watcom C/C++ | Open Source |
| .WPT | Corel | Fişiere text | WordPerfect Template | Cube 2 Sauerbraten | Open Source |
| .WR! | IBM | Fişiere foi de calcul | Lotus 1-2-3 Spreadsheet | Gnumeric | Open Source |
| .WRD | Open Source | Fişiere text | COREX Manually Verified Word Segmentation Data | COREX | Open Source |
| .WRL | Unknown Developer | Fişiere de imagini 3D | VRML World | FreeWRL | Open Source |
| .WRZ | Parallel Graphics | Fişiere de imagini 3D | Compressed VRML World File | FreeWRL | Open Source |
| .WS | MicroPro International Corp. | Fişiere text | WordStar Document | OpenEmu | Open Source |
| .WSC | Open Source | Fişiere de jocuri | WonderSwan Color Game ROM | Oswan | Open Source |
| .WSIM | Open Source | Fișiere web | FirstStop WebSearch Import Module | FirstStop WebSearch | Open Source |
| .WSR | Genius Media Group | Fişiere de date | Crossword Genius Data | FirstStop WebSearch | Open Source |
| .WUL | Open Source | Fișiere neobișnuite | WinUHA Language File | WinUHA | Open Source |
| .WV | David Bryant | Fişiere audio | WavPack Audio File | XMMS | Open Source |
| .WVC | Open Source | Fişiere audio | WavPack Correction File | WavPack | Open Source |
| .WVE | Wondershare Software Co., Ltd. | Fişiere video | Wondershare Filmora Project File | SoX | Open Source |
| .WVL | Open Source | Fişiere de imagini rastru | Wavelet Image | DjVu Reader | Open Source |
| .WVM | Google | Fişiere video | Google Play Video File | HandBrake | Open Source |
| .WX | Open Source | Fişiere de rezervă | Wanam Xposed Backup File | Wanam Xposed | Open Source |
| .WXM | Open Source | Fișiere neobișnuite | wxMaxima Batch File | wxMaxima | Open Source |
| .WXP | Open Source | Fişiere video | Wax 2.0 Project | DebugMode Wax | Open Source |
| .WXR | Open Source | Fişiere de date | WxWindgets Resource Data | wxWidgets | Open Source |
| .WZ | Nexon | Fişiere de jocuri | MapleStory Game Data File | Warzone 2100 | Open Source |
| .X13 | DarXabre | Fişiere de jocuri | Hooligans Game Archive File | Dragon UnPACKer | Open Source |
| .X64 | Commodore International | Fişiere de imagini de disc | Commodore 64 Disk Image | VICE | Open Source |
| .XA | Electronic Arts | Fişiere audio | The Sims Audio File | PSMplay | Open Source |
| .XA2 | Csabo | Fişiere de jocuri | XWE Data File | XWE | Open Source |
| .XAC | Tilted Mill Entertainment | Fişiere de jocuri | SimCity Societies Game File | GnuCash | Open Source |
| .XAF | Autodesk, Inc. | Fişiere de imagini 3D | 3ds Max XML Animation File | Cal3DViewer | Open Source |
| .XAR | Magix Software GmbH | Fişiere de imagini vectoriale | Xara Xtreme Drawing | Xara Xtreme for Linux | Open Source |
| .XBEL | Python Software Foundation | Fișiere web | XBEL Bookmarks File | Arora | Open Source |
| .XBL | Open Source | Fişiere de programator | XBLite Source Code File | XBLite | Open Source |
| .XBM | Unknown Developer | Fişiere de imagini rastru | X11 Bitmap Graphic | IrfanView | Open Source |
| .XCF | Gimpel Software | Fişiere de imagini rastru | GIMP Image File | IrfanView | Open Source |
| .XDC | Adobe Systems Incorporated | Fişiere de setări | Adobe Acrobat Printer Description | DarkCrypt IV | Open Source |
| .XDELTA | Open Source | Fişiere comprimate | Xdelta Binary Differential File | xdelta | Open Source |
| .XDF | NASA | Fişiere de imagini de disc | Extended Disk Format Image | TunerPro | Open Source |
| .XEN | Activision | Fişiere de jocuri | Guitar Hero 3 Data File | Xenu's Link Sleuth | Open Source |
| .XGP | Open Source | Fişiere de date | Xfire Game Patcher File | XGP | Open Source |
| .XHD | Open Source | Fișiere neobișnuite | HappyFish XML Data File | HappyFish | Open Source |
| .XI | Starbreeze Studios | Fişiere audio | Fasttracker 2 Extended Instrument File | MilkyTracker | Open Source |
| .XKM | Open Source | Fişiere de date | X KeyBoard File | Linux | Open Source |
| .XL | Microsoft Corporation | Fişiere foi de calcul | Excel Spreadsheet | XBLite | Open Source |
| .XLF | Open Source | Fişiere de date | XLIFF Document | OmegaT | Open Source |
| .XLS | Microsoft Corporation | Fişiere foi de calcul | Microsoft Excel 97 To 2003 Spreadsheet | Gnumeric | Open Source |
| .XM | Starbreeze Studios | Fişiere audio | FastTracker 2 Extended Module | ModPlug Player | Open Source |
| .XMCD | Parametric Technology Corporation | Fişiere de date | Mathcad Worksheet File | SMath Studio | Open Source |
| .XMF | Open Source | Fişiere de imagini 3D | Cal3D XML Mesh File | Cal3DViewer | Open Source |
| .XML | Wattle Software | Fişiere de date | XML File | AbiWord | Open Source |
| .XMZ | Starbreeze Studios | Fişiere audio | FastTracker 2 Extended Module | ModPlug Player | Open Source |
| .XP3 | Open Source | Fişiere de jocuri | KiriKiri Package File | XP3 / Kirikiri tools | Open Source |
| .XPF | Open Source | Fişiere audio | Linux MultiMedia Studio Preset File | LMMS | Open Source |
| .XPM | XnSoft | Fişiere de imagini rastru | X11 Pixmap Graphic | IrfanView | Open Source |
| .XPY | Open Source | Fişiere de setări | XPY Settings File | XPY | Open Source |
| .XQL | Open Source | Fişiere de programator | XML Query Language File | MacVim | Open Source |
| .XR | Red Hat | Fişiere de programator | Cygwin Ld-scripts Data | Cygwin | Open Source |
| .XR2 | Open Source | Fişiere de date | Xrecode II Registration | Xrecode | Open Source |
| .XRF | Open Source | Fişiere de imagini 3D | Cal3D XML Materials File | Cal3DViewer | Open Source |
| .XRL | SAP | Fişiere de date | PowerDesigner Report File | XML Résumé Library | Open Source |
| .XS3 | Open Source | Fişiere foi de calcul | XESS Worksheet | Xess | Open Source |
| .XS4 | Open Source | Fişiere foi de calcul | XESS Worksheet | Xess | Open Source |
| .XS5 | Open Source | Fişiere foi de calcul | XESS Worksheet | Xess | Open Source |
| .XSF | Microsoft Corporation | Fişiere de date | InfoPath Form Definition File | Cal3DViewer | Open Source |
| .XSP | Open Source | Fişiere audio | Kodi Smart Playlist File | Kodi | Open Source |
| .XSPF | VideoLAN | Fişiere audio | XSPF Playlist File | Clementine | Open Source |
| .XVG | Open Source | Fişiere text | Grace Document | GRACE | Open Source |
| .XVID | DivX, LLC. | Fişiere video | Xvid-Encoded Video File | Eltima Elmedia Player | Open Source |
| .XVO | Open Source | Fişiere de date | RatDVD Internal File | RatDVD | Open Source |
| .XYZ | SourceForge | Fişiere de date | Molecule Specification File | Avogadro | Open Source |
| .XZ | Various Developers | Fişiere comprimate | XZ Compressed Archive | ExtractNow | Open Source |
| .Y | Microsoft Corporation | Fişiere de imagini rastru | Subsampled Raw YUV Image | AbiWord | Open Source |
| .YAB | Open Source | Fişiere de programator | Yabasic Source Code | Yabasic | Open Source |
| .YDK | Open Source | Fişiere de jocuri | Yu-Gi-Oh! Deck File | YGOPRO | Open Source |
| .YENC | Open Source | Fişiere criptate | yEnc File | yDec | Open Source |
| .YGD | Open Source | Fişiere audio | YouGooDai Playlist File | YouGooDai | Open Source |
| .YM | Atari Corporation | Fişiere audio | Atari ST Audio File | ST-Sound | Open Source |
| .YMP | Open Source | Fişiere de programator | YaST Metapackage File | YaST | Open Source |
| .YNC | Open Source | Fişiere criptate | yEnc Encoded File | yDec | Open Source |
| .YSP | Open Source | Fişiere de imagini rastru | BYOB Sprite File | Snap! | Open Source |
| .YUV | WinXMedia Software | Fişiere video | YUV Video File | IrfanView | Open Source |
din 17 
