| .KIT | Bryan | Ficheiros Web | CodeKit File | CodeKit | Bryan |
| .LASSO | LassoSoft | Ficheiros Web | Lasso Database-Driven Web Page | Safari | Apple |
| .LESS | Adobe Systems Incorporated | Ficheiros Web | LESS Style Sheet | Adobe Dreamweaver | Adobe Systems Incorporated |
| .LIST | Open Source | Ficheiros Web | APT List File | Advanced Package Tool (APT) | Open Source |
| .M2L | Maxthon | Ficheiros Web | Maxthon Language Package | Maxthon Cloud Browser | Maxthon |
| .MAFF | Mozilla | Ficheiros Web | Mozilla Archive Format File | Mozilla Firefox | Mozilla |
| .MAI | Microsoft Corporation | Ficheiros Web | Microsoft Mail File | Microsoft Mail | Microsoft Corporation |
| .MAP | id Software | Ficheiros Web | Quake Engine Map File | Valve Hammer Editor | Valve |
| .MAPX | Mapjects | Ficheiros Web | Mapjects Client Webparts File | Mapjects GRYD | Mapjects |
| .MASTER | Microsoft Corporation | Ficheiros Web | ASP.NET Master Page | Microsoft Visual Studio | Microsoft Corporation |
| .METALINK | JDownloader Team | Ficheiros Web | Metalink 3.0 Download Descriptor File | Free Download Manager | Free Download Manager.ORG |
| .MHP | Open Source | Ficheiros Web | Maths Helper Plus File | Maths Helper Plus | Open Source |
| .MHT | Various Developers | Ficheiros Web | MHTML Web Archive | Internet Explorer | Microsoft Corporation |
| .MHTM | Microsoft Corporation | Ficheiros Web | Mime HTML (MHTML) File | Internet Explorer | Microsoft Corporation |
| .MHTML | Microsoft Corporation | Ficheiros Web | Mime HTML (MHTML) File | Internet Explorer | Microsoft Corporation |
| .MJZ | Avast Software | Ficheiros Web | Trojan.Win32.Agent.mjz Data | Avast Antivirus | Avast Software |
| .MOZ | Mozilla | Ficheiros Web | Mozilla Cache File | Mozilla Firefox | Mozilla |
| .MSB | Oracle Corporation | Ficheiros Web | Oracle Binary Message File | Oracle Database | Oracle Corporation |
| .MSPX | Microsoft Corporation | Ficheiros Web | Microsoft ASP.NET Web Page | Safari | Apple |
| .MUSE | Adobe Systems Incorporated | Ficheiros Web | Adobe Muse Website Project | Adobe Muse CC | Adobe Systems Incorporated |
| .MVC | Collectorz.com | Ficheiros Web | Movie Collector Catalog | Movie Collector | Collectorz.com |
| .MVR | IBM | Ficheiros Web | IBM HotMedia Multimedia File | HotMedia | IBM |
| .NA2 | Mozilla | Ficheiros Web | Netscape Address Book File | SeaMonkey | Mozilla |
| .NOD | NetObjects | Ficheiros Web | NetObjects Fusion File | NetObjects Fusion | NetObjects |
| .NZB | Various Developers | Ficheiros Web | NewzBin Usenet Index File | NewsLeecher | Art Systems LLC |
| .OBML | Opera Software | Ficheiros Web | Opera Mini Saved Web Page | Opera Mini | Opera Software |
| .OBML16 | Opera Software | Ficheiros Web | Opera Mini Saved Web Page | Opera Mini | Opera Software |
| .OPML | The Omni Group | Ficheiros Web | Outline Processor Markup Language File | CS Odessa ConceptDraw MINDMAP | CS Odessa |
| .OTH | Apache Software Foundation | Ficheiros Web | OpenDocument HTML Template | Apache OpenOffice | Apache Software Foundation |
| .P12 | RSA Laboratories | Ficheiros Web | Personal Information Exchange File | Adobe Acrobat DC | Adobe Systems Incorporated |
| .P7 | Open Source | Ficheiros Web | PKCS #7 Digital Certificate File | OpenSSL | Open Source |
| .P7B | Microsoft Corporation | Ficheiros Web | PKCS #7 Certificate File | Microsoft Windows | Microsoft Corporation |
| .P7C | Microsoft Corporation | Ficheiros Web | PKCS #7 Certificate File | Microsoft Windows | Microsoft Corporation |
| .PAC | NetScape | Ficheiros Web | Proxy Auto-Config File | Internet Explorer | Microsoft Corporation |
| .PAG | Microsoft Corporation | Ficheiros Web | Visual Basic Property PAGe File | Microsoft Visual Basic | Microsoft Corporation |
| .PAGE | Hybrid Server Pages Group | Ficheiros Web | HybridJava Web Page | Notepad++ | Don Ho |
| .PEM | Microsoft Corporation | Ficheiros Web | Privacy Enhanced Mail Certificate | Microsoft IIS | Microsoft Corporation |
| .PHP | Panic | Ficheiros Web | PHP Source Code File | Microsoft Notepad | Microsoft Corporation |
| .PHP2 | Open Source | Ficheiros Web | PHP 2 Web Page | Vim | Bram Moolenaar |
| .PHP3 | Open Source | Ficheiros Web | PHP 3 Web Page | MacroMates TextMate | MacroMates |
| .PHP4 | Open Source | Ficheiros Web | PHP 4 Web Page | MacroMates TextMate | MacroMates |
| .PHP5 | Open Source | Ficheiros Web | PHP 5 Web Page | MacroMates TextMate | MacroMates |
| .PHT | Microsoft Corporation | Ficheiros Web | Partial Hypertext | Internet Explorer | Microsoft Corporation |
| .PHTM | The Catalina Group | Ficheiros Web | PHP-Based Web Page | Microsoft Notepad | Microsoft Corporation |
| .PHTML | Opera Software | Ficheiros Web | PHP Web Page | Apache Tomcat | Apache Software Foundation |
| .PIM | Avid Technology | Ficheiros Web | Pro Tools Controller Plug-in Mappings File | Avid Pro Tools | Avid Technology |
| .PMX | Yu Higuchi | Ficheiros Web | MikuMikuDance Model File | MikuMikuDance | Yu Higuchi |
| .PNQ | Mail.Ru | Ficheiros Web | ICQ Instant Message File | ICQ | Mail.Ru |
| .PPTMHTML | Microsoft Corporation | Ficheiros Web | Microsoft PowerPoint MIME HTML Presentation | Microsoft PowerPoint | Microsoft Corporation |
| .PRF | Microsoft Corporation | Ficheiros Web | Outlook Profile File | Microsoft Outlook 2016 | Microsoft Corporation |
| .PRO | Adobe Systems Incorporated | Ficheiros Web | Adobe Proto Design File | Adobe Dreamweaver | Adobe Systems Incorporated |
| .PSP | Corel Corporation | Ficheiros Web | PaintShop Pro Image | Corel Painter | Corel |
| .PTW | Autodesk, Inc. | Ficheiros Web | AutoCAD Publish To Web File | Autodesk AutoCAD | Autodesk, Inc. |
| .PUB | Microsoft Corporation | Ficheiros Web | Microsoft Publisher Document | LibreOffice | The Document Foundation |
| .QBO | Intuit, Inc. | Ficheiros Web | QuickBooks Online Bank Statement File | FreshBooks | FreshBooks Company |
| .QF | Nokia | Ficheiros Web | Nokia (Ovi) Maps Version Data | Microsoft Notepad | Microsoft Corporation |
| .QRM | Armangil Software | Ficheiros Web | Qworum Message File | Internet Explorer | Microsoft Corporation |
| .QWD | id Software | Ficheiros Web | QuakeWorld Demo File | QuakeWorld | id Software |
| .QWT | Quark Software Inc. | Ficheiros Web | QuarkXpress Web Document Template | QuarkXPress | Quark Software Inc. |
| .RCG | Neil Fraser | Ficheiros Web | Recog Character Recognition Set | Recog | Neil Fraser |
| .RHTML | Yukihiro “Matz” Matsumoto | Ficheiros Web | Ruby HTML Web Page | MacroMates TextMate | MacroMates |
| .RJS | Yukihiro “Matz” Matsumoto | Ficheiros Web | Ruby Javascript File | Notepad++ | Don Ho |
| .RSS | Various Developers | Ficheiros Web | Rich Site Summary | Mozilla Firefox | Mozilla |
| .RT | RealNetworks | Ficheiros Web | RealText Streaming Text File | VLC Media Player | VideoLAN |
| .RW3 | Realmac Software | Ficheiros Web | RapidWeaver 3 Site File | RapidWeaver | Realmac Software |
| .RWP | Realmac Software | Ficheiros Web | RapidWeaver Package | RapidWeaver | Realmac Software |
| .S1H | Oracle Corporation | Ficheiros Web | Sealed HTML Document | Unknown Software | Unknown Developer |
| .SCSS | Sublime HQ Pty Ltd | Ficheiros Web | Syntactically Awesome Stylesheets Syntax Data | Adobe Dreamweaver | Adobe Systems Incorporated |
| .SHT | The Document Foundation | Ficheiros Web | HTML File With Server Side Includes | LibreOffice | The Document Foundation |
| .SHTML | Sublime HQ Pty Ltd | Ficheiros Web | Server Side Include HTML File | Microsoft Notepad | Microsoft Corporation |
| .SITE | Adobe Systems Incorporated | Ficheiros Web | GoLive Website Project File | Adobe GoLive | Adobe Systems Incorporated |
| .SITEMAP | Microsoft Corporation | Ficheiros Web | ASP.NET Site Map File | Microsoft Visual Studio | Microsoft Corporation |
| .SPAM | Unknown Developer | Ficheiros Web | Spam E-mail Message | Unknown Software | Unknown Developer |
| .SPC | Various Developers | Ficheiros Web | Software Publisher Certificate File | OpenSSL | Open Source |
| .SPM | Corel | Ficheiros Web | Corel WordPerfect Data | Corel WordPerfect | Corel |
| .SRF | NewTek | Ficheiros Web | LightWave Surface File | LightWave 3D | NewTek |
| .SSH | Microsoft Corporation | Ficheiros Web | Microsoft Internet Explorer Style Sheet | Internet Explorer | Microsoft Corporation |
| .SSP | Scala | Ficheiros Web | Scala Server Page | Scalate | Open Source |
| .STC | Adobe Systems Incorporated | Ficheiros Web | Contribute Connection Key File | Adobe Contribute 6.5 | Adobe Systems Incorporated |
| .STL | 3D Systems | Ficheiros Web | Stereolithography File | Creo Parametric 3D Modeling Software | PTC |
| .STM | Microsoft Corporation | Ficheiros Web | Exchange Streaming Media File | Microsoft Exchange Server | Microsoft Corporation |
| .STP | Unknown Developer | Ficheiros Web | STEP 3D CAD File | CATIA | Dassault Systèmes |
| .SVC | Microsoft Corporation | Ficheiros Web | WCF Web Service File | Microsoft Internet Information Services (IIS) | Microsoft Corporation |
| .SVR | Superscape | Ficheiros Web | Compressed Virtual World | Safari | Apple |
| .SWZ | Adobe Systems Incorporated | Ficheiros Web | Adobe Flash Player Cache File | Adobe Flash Player | Adobe Systems Incorporated |
| .TVVI | TitanTV, Inc. | Ficheiros Web | TitanTV Television Listing File | ArcSoft TotalMedia Backup & Record | ArcSoft |
| .TWF | ESRI | Ficheiros Web | ArcView World Coordinates | ArcView | ESRI |
| .UCF | Cisco Systems | Ficheiros Web | WebEx Media File | WebEx Meetings | Cisco Systems |
| .URL | Microsoft Corporation | Ficheiros Web | Internet Shortcut | Microsoft Notepad | Microsoft Corporation |
| .VBD | Microsoft Corporation | Ficheiros Web | Visual Basic ActiveX Document | Microsoft Visual Studio | Microsoft Corporation |
| .VBHTML | Microsoft Corporation | Ficheiros Web | Microsoft Visual Studio ASP.NET Web Page | Microsoft Visual Studio | Microsoft Corporation |
| .VBM | Veeam Software | Ficheiros Web | Veeam Backup Metadata File | Veeam Backup & Replication | Veeam Software |
| .VDW | Microsoft Corporation | Ficheiros Web | Microsoft Visio Web Drawing | Microsoft Office | Microsoft Corporation |
| .VLP | Interscape | Ficheiros Web | LiveSite Project | Valadeo LiveSite | Interscape |
| .VMSG | VMware | Ficheiros Web | VMware Application Message File | VMware Workstation | VMware |
| .VRML | Open Source | Ficheiros Web | Virtual Reality Modeling Language 3D World | FreeWRL | Open Source |
| .VRT | Superscape | Ficheiros Web | Virtual World | Internet Explorer | Microsoft Corporation |
| .VSDISCO | Microsoft Corporation | Ficheiros Web | DISCO Dynamic Discovery Document | Microsoft Visual Studio | Microsoft Corporation |
| .VSY | Open Source | Ficheiros Web | VNC Spy Log File | VNC Spy | Open Source |
| .VX | Opera Software | Ficheiros Web | Opera Browser Data | Opera | Opera Software |
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