| .x | Lex Language Source Code |
| .x-png | Portable (Public) Network Graphic Bitmap |
| .x01 | Corel Paradox Secondary Index |
| .x02 | Corel Paradox Secondary Index |
| .x03 | Corel Paradox Secondary Index |
| .x04 | Corel Paradox Secondary Index |
| .x05 | Corel Paradox Secondary Index |
| .x06 | Corel Paradox Secondary Index |
| .x07 | Corel Paradox Secondary Index |
| .x08 | Corel Paradox Secondary Index |
| .x09 | Corel Paradox Secondary Index |
| .x1 | X1 Desktop Search Saved Search |
| .x10 | X Window Bitmap Dump |
| .x11 | X Window System Bitmap Image |
| .x13 | Hooligans Game Archive |
| .x20 | XTree Gold For Dos Help |
| .x32 | Adobe Xtra Format |
| .x3a | MOTIF XF |
| .x3d | X3D Format |
| .x3db | X3D Binary Format |
| .x3dv | Web3D X3D Graphics Image |
| .x3f | Sigma Camera RAW Picture Format |
| .x3g | MakerBot MakerWare Document |
| .x40 | XtreeGold Dos Help |
| .x4k | XML4King Configuration Format |
| .x50 | XtreeGold Dos Help |
| .x60 | XTree Gold For Dos Help |
| .x64 | Commodore 64 Emulator Disk Image |
| .x70 | XTree Gold For Dos Help |
| .x80 | Xtree Gold Dos Help |
| .x90 | XTree Gold For Dos Help |
| .xa | Sony PlayStation Audio/video Format |
| .xa0 | Xtree Gold Dos Help |
| .xab | Microsoft Outlook Express Address Book |
| .xac | SimCity Societies Game |
| .xad | EXotic ADlib Sound Format |
| .xadd | Expression Web Add-in |
| .xadml | Amiga Forever XADML |
| .xaf | Xml Compatible Animation Format |
| .xaiml | XAIML Database Format |
| .xaml | Windows Markup File |
| .xamlx | XAMLX Document Format |
| .xan | Worms 3D Map Format |
| .xap | Microsoft Silverlight Application Package Format |
| .xappl | Virtual Application Studio XML Application Configuration Format |
| .xar | Xara Vector Drawing Format |
| .xarc | The Longest Journey Audio |
| .xas | PTC Pro/Engineer Assembly Format |
| .xav | Final Draft AV Document |
| .xavc | Sony XAVC Video Format |
| .xb0 | Xtree Gold Dos Help |
| .xba | OpenOffice.org Basic Module Format |
| .xbap | Microsoft Silverlight Application Package |
| .xbb | DVIPDFMx Output |
| .xbc | SMART Notebook Format |
| .xbd | JAXB Schema |
| .xbdoc | Xiosis Scribe Document |
| .xbe | Xbox Executable Format |
| .xbel | XBEL Bookmarks Format |
| .xbf | Emperor Battle For Dune |
| .xbk | SMART Notebook Format |
| .xbl | Extensible Binding Language Format |
| .xblr | Output Raw XBRL |
| .xbm | X Windows System Bitmap Image |
| .xbmml | Braille Music Score |
| .xbmp | Area 51 Game |
| .xbn | Xnick Nick Backup |
| .xbplate | Xiosis Scribe Template |
| .xbrl | Extensible Business Reporting Language |
| .xbsav | Mass Effect 2 For Xbox Saved Game Format |
| .xbt | SMART Notebook Template Format |
| .xbx | Xbox Icon Or Picture |
| .xc0 | Xtree Gold Dos Help |
| .xc3 | Cast3D 3D Scene |
| .xcappdata | Apple Xcode Application Data Format |
| .xcarchive | Xcode Archive |
| .xcconfig | Apple Xcode Configuration Settings |
| .xcdatamodel | Xcode Core Data Model Format |
| .xcdatamodeld | Xcode Core Data Model Format |
| .xcel | Microsoft Excel For Mac Spreadsheet |
| .xcf | GIMP XCF Bitmap Image Format |
| .xch | LinkAssistant Project Settings |
| .xci | Adobe Reader Font Mapping |
| .xcl | XTree For Windows Script |
| .xcm | CmapTools Exported Concept Map |
| .xco | Xilinx CORE Generator Log |
| .xcode | Xcode Development Project Format |
| .xcodeplugin | Apple Xcode Extension |
| .xcodeproj | XCode Project Format |
| .xcof | Mac OS Object Library |
| .xcon | Conceal Encrypted Data |
| .xcorpus | Xaira Corpora |
| .xcp | XLNT Script Command |
| .xcplugin | Apple Xcode Extension |
| .xcplugindata | Xcode Plug-in Data |
| .xcr | Warlords Battlecry Game |
| .xcscheme | Apple Xcode Scheme |
| .xcsl | CineStyle Color Correction Settings Format |
| .xcsnapshots | Xcode Snapshot |
| .xct | XVI32 Conversion |
| .xctl | LabVIEW XControls |
| .xcu | OpenOffice.org Extension Control Format |
| .xcuserstate | Xcode |
| .xcworkspace | Xcode Workspace Format |
| .xd0 | XtreeGold Dos Help |
| .xda | Sencha Architect Project |
| .xdb | Norton AntiVirus Update Format |
| .xdc | Total Commander With DarkCrypt IV Plug-in Encrypted |
| .xdf | Externally Defined Function |
| .xdfl | XDFL Configuration |
| .xdi | WinArchiver Compressed ISO Image Format |
| .xdl | MS SQL Server XML Schema Format |
| .xdo | Oracle BI Publisher Resource Tracking |
| .xdoc | QuarkXPress 3.0 Document |
| .xdoclet | JBoss XDoclet Reference |
| .xdp | Acrobat XML Data Package Format |
| .xdr | XML Data Reduced Format |
| .xds | LCDStudio Design Format |
| .xdt | Win-Test Extra Data |
| .xdu | Backdoor.Win32.PcClient.xdu |
| .xdv | XeTeX |
| .xdw | DocuWorks Document Format |
| .xe0 | XtreeGold Dos Help |
| .xef | X-Genics EManager Form Data Format |
| .xej | Microsoft Expression Encoder Job Format |
| .xel | Microsoft Expression Encoder 3.0 Live Jobs Format |
| .xem | Sybase PowerDesigner Model Definition Format |
| .xen | Activision Guitar Hero 3 Data Format |
| .xensearch | XenCenter Saved Search Format |
| .xeo | Signwave Auto-Illustrator Extension |
| .xep | EManager File Packing Definition |
| .xeq | Sage MAS 90 Data |
| .xer | Primavera Project Management Propriety Exchange Format |
| .xes | X-Genics EManager Skins Definition |
| .xesc | Microsoft Expression Encoder Screen Capture Format |
| .xet | X-Genics EManager Process Definition |
| .xev | X-Genics EManager Auto-update Format |
| .xevgenxml | Adobe Dreamweaver |
| .xex | Xbox 360 Executable Format |
| .xez | X-Genics EManager Template Package |
| .xfa | OneCncXR CAD |
| .xfbin | Naruto Shippuden: Ultimate Ninja Storm 2 |
| .xfc | X-Fonter Font Collection |
| .xfd | Adobe XFDL Format XML Form Format |
| .xfdf | Adobe Acrobat Forms Document |
| .xfdl | XFDL Format |
| .xff | XFRX Database Output |
| .xfi | XICE Desktop Encrypted |
| .xfl | Adobe Flash Exchange Format |
| .xfm | OmniForm XML |
| .xfn | Corel Ventura Printer Font |
| .xfo | XSL-FO Formatted Form |
| .xfp | Microsoft SharePoint Extending Form Library Properties |
| .xfr | Ventura Publisher Bitmap Editor Font Format |
| .xfs | Gunbound Format |
| .xft | Adobe Form Designer Form |
| .xfz | French FlashCards Vocabulary |
| .xg0 | Corel Paradox Secondary Index |
| .xg1 | Corel Paradox Secondary Index |
| .xg2 | Corel Paradox Secondary Index |
| .xg3 | Corel Paradox Secondary Index |
| .xg4 | Corel Paradox Secondary Index |
| .xg5 | Corel Paradox Secondary Index |
| .xga | Diamond Mind Baseball Game Account Information |
| .xgd | Xbox 360 Game Disc Layout |
| .xgl | XGL 3D CAD Model |
| .xgll | EASE SpeakerLab Text |
| .xgml | Graph Modeling Language XML Format |
| .xgmml | XGMML Graph Format |
| .xgo | GeoConcept Add-on |
| .xgp | Xfire Profile Patcher Game List Format |
| .xgs | Disk Image Format |
| .xhb | HomeBank Data |
| .xhp | OpenOffice.org Extension Help Format |
| .xht | Extensible HyperText Markup Language Format |
| .xhtm | Extensible HTML Format |
| .xhtml | Extensible HTML Format |
| .xi | Fastracker 2.0 Instrument Format |
| .xib | Apple Interface Builder Format |
| .xif | ScanSoft Pagis Format |
| .xig | XML Instance Generator |
| .xil | Xilize |
| .xilinc | Xilize Defintion |
| .xilize | Xilize Configuration |
| .xim | X11 Xim Toolkit Bitmap |
| .xin | OmniMark Include |
| .xip | Xbox Dashboard |
| .xise | Xilinx ISE Project Format |
| .xiso | Xbox ISO |
| .xit | SpatialAnalyzer |
| .xit64 | SpatialAnalyzer |
| .xix | IIS NNTP Subject Lists |
| .xiz | Ximinez |
| .xjb | OEPE JAXB Wizard Bindings |
| .xjt | Compressed GIMP Image |
| .xkm | X KeyBoard |
| .xl | Microsoft Excel Spreadsheet Format |
| .xla | Microsoft Excel Add-in Format |
| .xla5 | Microsoft Excel 5 For Mac Add-in |
| .xla8 | Microsoft Excel 98 For Mac Add-in |
| .xlam | Microsoft Excel 2007/2010 Open XML Macro-enabled Add-in Format |
| .xlamenx | Egis Encrypted Excel XLAM |
| .xla_ | Microsoft Excel 4 For Mac Add-in |
| .xlb | Microsoft Excel Toolbars Format |
| .xlb4 | Microsoft Excel 4 For Mac Toolbars |
| .xlb5 | Microsoft Excel 5 For Mac Toolbars |
| .xlb8 | Microsoft Excel 98 For Mac Toolbars |
| .xlbn | Microsoft Excel 1 For Mac Toolbars |
| .xlc | Microsoft Excel Chart Format |
| .xlc3 | Microsoft Excel 3 For Mac Chart |
| .xlc4 | Microsoft Excel 4 For Mac Chart |
| .xlc_ | Microsoft Excel 2 For Mac Chart |
| .xld | Microsoft Excel Dialogue Format |
| .xldb | AQUA Data |
| .xlf | XLIFF Document Format |
| .xlg | AutoCAD External Reference Log |
| .xlgc | ExpressK Database Format |
| .xli | SIEMENS PLM Software NX 7.5 Log |
| .xliff | XLIFF Localization Format |
| .xlk | Microsoft Excel Backup Format |
| .xll | Microsoft Excel Add-in Format |
| .xll_ | Microsoft Excel 4 For Mac Add-in |
| .xlm | Microsoft Excel Macro Format |
| .xlm3 | Microsoft Excel 3 For Mac Macro |
| .xlm4 | Microsoft Excel 4 For Mac Macro |
| .xlmv | Thunder Mall Video Format |
| .xlmx | Microsoft Excel Macro-enabled Spreadsheet |
| .xlm_ | Microsoft Excel 2 For Mac Macro |
| .xlnk | XML Link Format |
| .xlo | Autodesk Inventor Export Journal |
| .xlpf | Microsoft Excel For Mac Setting |
| .xlr | Microsoft Works Spreadsheet Or Chart Format |
| .xls | Microsoft Excel 97 To 2003 Workbook Format |
| .xls3 | Microsoft Excel 3 For Mac Spreadsheet |
| .xls4 | Microsoft Excel 4 For Mac Spreadsheet |
| .xls5 | Microsoft Excel 5 For Mac Spreadsheet |
| .xls8 | Microsoft Excel 98 For Mac Spreadsheet |
| .xlsb | Microsoft Excel 2007/2010 Binary Workbook Format |
| .xlsenx | Egis Encrypted Excel XLS |
| .xlshtml | Microsoft Office Excel HTML Document Format |
| .xlsm | Microsoft Excel 2007/2010 Open XML Macro-enabled Workbook Format |
| .xlsmhtml | Microsoft Excel MIME HTML Spreadsheet Format |
| .xlsx | Microsoft Excel 2007, Excel 2010 And Excel 2013 Open XML Workbook Format |
| .xlsxenx | Egis Encrypted Excel XLSX |
| .xls_ | Microsoft Excel For Mac Spreadsheet |
| .xlt | Microsoft Excel 97 To 2003 Workbook Template Format |
| .xlthtml | Microsoft Office Excel HTML Template Format |
| .xltm | Microsoft Excel 2007/2010 Open XML Macro-enabled Workbook Template Format |
| .xltx | Microsoft Excel 2007/2010 Open XML Workbook Template Format |
| .xlv | Microsoft Excel VBA Module Format |
| .xlw | Microsoft Excel Workspace Format |
| .xlw3 | Microsoft Excel 3 For Mac Workbook |
| .xlw4 | Microsoft Excel 4 For Mac Workbook |
| .xlw5 | Microsoft Excel 5 For Mac Workbook |
| .xlw_ | Microsoft Excel 2 For Mac Workbook |
| .xlxml | Microsoft Excel XML Worksheet |
| .xlz | Crossword Power Tools Crossword Library |
| .xm | FastTracker 2 Instrument |
| .xmap | XMind 2007/2008 Workbook |
| .xmb | Lucas Arts X-Wing Mission Briefing Format |
| .xmc | Lingoes Configuration |
| .xmcd | PTC Mathcad Worksheet Format |
| .xmcdz | PTC Mathcad Compressed Worksheet Format |
| .xmct | Mathcad Template Format |
| .xmd | GameJack Virtual CD Or DVD Image Format |
| .xme | GME |
| .xmef | TextMap Evidence Format |
| .xmf | CDRWin Virtual CD Image Format |
| .xmg | The Longest Journey XMG |
| .xmi | Miles Sound System Extended MIDI Files |
| .xmind | XMind Workbook Format |
| .xmit | IBM XMIT Data |
| .xml | XML Document Format |
| .xml-prev | VirtualBox XML Settings Backup |
| .xmla | XML For Analysis Source |
| .xmljet | Eclipse JET XML Template |
| .xmlper | LeCroy Binary Waveform Format |
| .xmls | Microsoft Excel 2003 XML |
| .xmlx | Excel Spreadsheet |
| .xmm | 3ds Max XML Animation Map Format |
| .xmmap | MindManager XML Map Format |
| .xmmas | MindManager XML Theme |
| .xmmat | MindManager XML Template |
| .xmo | Adobe Authorware Movie Driver |
| .xmod | Datawatch Monarch Model |
| .xmp | Adobe Extensible Metadata Platform Format |
| .xmpses | Adobe Premiere Elements |
| .xmpskin | XMPlay Skin |
| .xmpz | Miradi XML Project Format |
| .xms | Microsoft EXtended Memory Specification |
| .xmt | XMind Workbook Template |
| .xmta | Microsoft Visual Studio XMTA Document |
| .xmv | Microsoft Xbox Video Format |
| .xmx | AutoCAD External Message Compiled |
| .xmz | Fasttracker 2 Extended Module Format |
| .xn | Cygnus Ld-scripts |
| .xnb | XNA Game Studio Express XNA Framework Content Pipeline Binary Format |
| .xnd | ExNode Download |
| .xnf | Extensible Numerical |
| .xnk | Microsoft Exchange Shortcut Format |
| .xnode | LabVIEW |
| .xnp | XnView Addon |
| .xnt | QuarkXPress Extension Format |
| .xnv | NVision Layout |
| .xob | EasyBuilder 8000 Compiled Code |
| .xof | RenderMorphics Reality Lab 3D Image Format |
| .xojo_binary_menu | Xojo Binary Menu |
| .xojo_binary_project | Xojo Binary Project |
| .xojo_binary_window | Xojo Binary Window |
| .xojo_menu | Xojo Menu |
| .xojo_project | Xojo Programming Project |
| .xojo_window | Xojo Window |
| .xojo_xml_menu | Xojo XML Menu |
| .xojo_xml_window | Xojo XML Window |
| .xol | Swiss Map Overlay Format |
| .xom | Worms 3D Object Format |
| .xoml | Windows Workflow Format |
| .xop | IGOR Pro Add-on |
| .xov | RapidForm XOV 3D Inspection/Model |
| .xp | WindowBlinds Temporary Format |
| .xp0 | SecretPhotos Puzzle Graphic Image |
| .xp2 | XPilot NG |
| .xp3 | KiriKiri Package Format |
| .xp4 | KiriKiri Package |
| .xpac | Sonic & Sega All-Stars Racing For PC Game Audio Archive |
| .xpaddercontroller | Xpadder Controller Layout Format |
| .xpadderprofile | Xpadder Settings |
| .xpb | XPB! Basic Source Code |
| .xpd | XML Pipeline Document Format |
| .xpdl | XPDL Module |
| .xpf | XProtector Project |
| .xpg | Autoplay Media Studio Exported Page |
| .xpgt | EPUB XML Stylesheet Page Template |
| .xpi | Firefox Browser Extension Format |
| .xpj | Micro Planner X-Pert Project Format |
| .xpk | PSpice Library Format |
| .xpku | Apple Mac OS X Universal Binary Package |
| .xpl | X-Plane Plug-in Format |
| .xpl2 | TerraExplorerPro LOD Parameter |
| .xpm | X11 Pixmap Graphic |
| .xpng | Portable (Public) Network Graphic Bitmap |
| .xpp | X++ Source Code Format |
| .xpr | PTC Pro/ENGINEER Part Format |
| .xpr3 | QuarkXpress 3.0 Mac |
| .xprj | Monarch XML Project |
| .xps | XML Paper Specification Format |
| .xps~ | WindowBlinds Temporary |
| .xpt | Mozilla Firefox Component |
| .xptin | Xpswmm Hydrology Data |
| .xpw | Accessible FormNet Fillable Form |
| .xpx | Intercon FormNet |
| .xpy | MarketBrowser |
| .xp~ | WindowBlinds Temporary |
| .xq | XQuery Format |
| .xql | XML Query Language Format |
| .xqm | XQuery Module |
| .xqt | SuperCalc Macro Spreadsheet Format |
| .xquery | XQuery Source Code Format |
| .xqy | XQuery Source Format |
| .xr | Cygnus Ld-scripts |
| .xrc | WxWidgets WxPython Resource |
| .xrd | Core Wars Data |
| .xrdml | PANalytical XRD Measurement Data XML |
| .xref | IBM AIX Cross Reference |
| .xrf | WordSearch Cross Reference Format |
| .xrff | Extensible Attribute-Relation File Format |
| .xrl | PowerDesigner Report |
| .xrm-ms | Microsoft Security Certificate |
| .xrns | Extended Renoise Song Format |
| .xrp | RationalPlan Format |
| .xrs | Dig It! Game |
| .xrx | Expression Encoder Media Profile Settings |
| .xry | XRY Data Format |
| .xs | Age Of Empires 3 Map AI Generator Format |
| .xs4 | XESS Worksheet |
| .xs5 | XESS Worksheet |
| .xsb | XACT Sound Bank |
| .xsc | Microsoft Visual Studio XSC Format |
| .xsd | XML Schema Description Format |
| .xsf | Microsoft Office InfoPath Format |
| .xsi | SOFTIMAGE|XSI 3D Model |
| .xsiaddon | SOFTIMAGE XSI Add-on Format |
| .xsl | XML Stylesheet Format |
| .xslic | XenServer License Format |
| .xslt | XSL Transform Format |
| .xsm | SimCity Societies Game |
| .xsn | Microsoft Office InfoPath Template Form Format |
| .xso | Expresso Project |
| .xsp | XBMC Smart Playlist Format |
| .xspf | XML Shareable Playlist Format |
| .xsql | Oracle XSQL Servlet Server Side |
| .xsr | FabTrol MRP |
| .xss | XML Stylesheet Format |
| .xsslog | Microsoft SharePoint WorkSpace Groove Log |
| .xssr | Microsoft SharePoint WorkSpace Groove |
| .xst | Microsoft Outlook Personal Folders Format |
| .xstb | TextBridge |
| .xstk | XStarter Task |
| .xsu | Fortran 77 Library |
| .xsvf | Xilinx Serial Vector Format |
| .xsx | Microsoft Visual Studio XML Schema Layout Format |
| .xt | FastTracker Music Track Format |
| .xtc | XTrkCAD Project |
| .xtd | XML Type Definition |
| .xterme | Winstep Extreme Theme |
| .xtf | EXtended Triton Format |
| .xtg | QuarkXpress Tags Format |
| .xtic | ActivInspire Ticker |
| .xtl | Vietcong Game Data Format |
| .xtm | CmapTools Exported Topic Map Format |
| .xtml | XML4web Virtual HTML Document |
| .xtmp | Avid Xpress Pro Template |
| .xtnd | Adobe Acrobat For Mac Plug-In |
| .xtodvd | ConvertXtoDVD Project |
| .xtp | XTreeGold Overlay |
| .xtra | Adobe Director Xtra |
| .xtreme | Winstep Xtreme Theme Pack Format |
| .xtrl | XTND Translator |
| .xtxt | Xtext |
| .xui | Xbox 360 Skin Format |
| .xul | Firefox XML User Interface Language Format |
| .xur | Xbox 360 Compiled Skin Format |
| .xv | Khoros Visualization Bitmap Image |
| .xv0 | Lattice XVL Structure Format |
| .xv2 | V-XVL Geometry |
| .xv3 | P-XVL Geometry Format |
| .xva | Citrix Xen Virtual Appliance Format |
| .xvct | VISE XML Project Format |
| .xvg | Grace Document |
| .xvid | XviD Codec |
| .xvl | EXtensible Virtual World Description Language Document |
| .xvm | VMware Console Configuration Format |
| .xvmconf | World Of Tanks Configuration Format |
| .xvo | RatDVD Internal |
| .xvu | BOClean Database Format |
| .xwb | XACT Wave Bank Format |
| .xwc | Starbreeze Sound |
| .xwd | X Window Window Screen Dump Or Bitmap |
| .xwf | OmniPage Workflow Format |
| .xwi | Star Wars: X-Wing Mission |
| .xwk | Crosstalk Keyboard Mapping Format |
| .xwm | The Elder Scrolls V: Skyrim Music |
| .xwma | XWMA Audio Compression Format |
| .xwmv | Microsoft Windows Media |
| .xwp | Xerox Writer Document |
| .xws | Xara Webstyle Format |
| .xx | XXEncoded Format |
| .xxd | Brixx Planner Calendar Format |
| .xxe | XXEncoded Format |
| .xxx | Compucon/Singer PSW Embroidery Design Format |
| .xy | XyWrite Document |
| .xy3 | XYWrite III Document |
| .xyp | XY Write III Plus Document |
| .xys | XYplorer Script Format |
| .xyw | XYWrite For Windows 3x/4.0 Document |
| .xyz | Molecule Specification Format |
| .xyze | Radiance Map |
| .xyzi | 3rdTech Scanner |
| .xyzrgb | 3rdTech XYZ RGB Graphic |
| .xyzv | Celestia Sampled Trajectory Format |
| .xz | XZ Utils Compressed Archive |
| .xzfx | ZipLogix ZipForm Format |
| .xzm | Slackware Linux Package |
| .x_b | Parasolid Document Format |
| .x_t | Parasolid File Format |
