| .TKP | MicroImages | File sviluppatore | MicroImages SML Script Standalone Application | TNTmips | MicroImages |
| .TLD | The Eclipse Foundation | File sviluppatore | Tag Library Descriptor File | Notepad++ | Don Ho |
| .TLH | Microsoft Corporation | File sviluppatore | Typelib Generated C/C++ Header File | Microsoft Visual Studio | Microsoft Corporation |
| .TLI | Microsoft Corporation | File sviluppatore | Typelib Generated C/C++ Inline File | Microsoft C/C++ | Microsoft Corporation |
| .TML | Odetics Broadcast | File sviluppatore | AIRO Timeline File Format | AIRO | Odetics Broadcast |
| .TMPL | Xfire, Inc. | File sviluppatore | Xfire User Interface Template | Xfire | Xfire, Inc. |
| .TNS | Texas Instruments, Inc. | File sviluppatore | TI-Nspire Document | Texas Instruments TI-Nspire Software | Texas Instruments, Inc. |
| .TOKEN | Microspot | File sviluppatore | Sandcastle Help File Builder Token File | Microsoft Sandcastle | Microspot |
| .TOM | Aptora | File sviluppatore | Total Office Manager Accounting Data | Total Office Manager | Aptora |
| .TPR | Pegasys | File sviluppatore | TMPGEnc Project File | Media Player Classic | Open Source |
| .TPT | Cerious Software | File sviluppatore | ThumbsPlus Thumbnail Template | ThumbsPlus | Cerious Software |
| .TPU | Borland | File sviluppatore | Turbo Pascal Unit | Turbo Pascal | Embarcadero Technologies |
| .TPX | DeLorme | File sviluppatore | DeLorme Topo Project File | Topo North America | Interscape |
| .TQS | Parasoft | File sviluppatore | Insure++ Data | Insure++ | Parasoft |
| .TR2 | Yadabyte | File sviluppatore | TomeRaider eBook File | TomeRaider | Yadabyte |
| .TRC | Microsoft Corporation | File sviluppatore | SQL Server Trace File | Microsoft SQL Server | Microsoft Corporation |
| .TRT | Galactix Software | File sviluppatore | Team Sports Scheduling System Report Template | Team Sports Scheduling System | Galactix Software |
| .TRU | Original Basic | File sviluppatore | True Basic Source | True Basic Bronze Edition | Original Basic |
| .TRX | Microsoft Corporation | File sviluppatore | Visual Studio Test Results File | Microsoft Visual Studio | Microsoft Corporation |
| .TS | Various Developers | File sviluppatore | Video Transport Stream File | Squared 5 MPEG Streamclip | Open Source |
| .TSQ | Microsoft Corporation | File sviluppatore | ODBC Script File | Microsoft ODBC Data Source Administrator | Microsoft Corporation |
| .TT | Microsoft Corporation | File sviluppatore | Visual Studio Text Template | Microsoft Visual Studio | Microsoft Corporation |
| .TTI | Delphi Softwares | File sviluppatore | Trojan File | Beast (Trojan Horse) | Delphi Softwares |
| .TTR | Interscape | File sviluppatore | TextTransformer Productions | TextTransformer | Detlef Meyer-Eltz |
| .TU | Holt Software | File sviluppatore | Turing Source File | Holt Software Turing | Holt Software |
| .TUR | Holt Software | File sviluppatore | Turing Program Source File | Microsoft Notepad | Microsoft Corporation |
| .TXG | ESRI | File sviluppatore | Georeference Subobject File | ERDAS Imagine | Hexagon Geospatial |
| .TXL | Open Source | File sviluppatore | TXL Source Code | Notepad++ | Don Ho |
| .TXS | Delphi Softwares | File sviluppatore | Beast (Trojan Horse) Data File | Beast (Trojan Horse) | Delphi Softwares |
| .TXX | National Library of Medicine | File sviluppatore | Insight Segmentation And Registration Toolkit Data File | Insight Segmentation and Registration Toolkit | Open Source |
| .TYB | Tyler Johnson | File sviluppatore | TY-Basic Source Code File | Ty-Basic | Tyler Johnson |
| .U2 | IBM | File sviluppatore | Telelogic Tau UML Model File | Rational Tau | IBM |
| .U2P | IBM | File sviluppatore | Telelogic Tau UML Program Text File | Rational Tau | IBM |
| .UAE | Interscape | File sviluppatore | WinUAE Configuration Data | WinUAE | Interscape |
| .UCLS | ObjectAid | File sviluppatore | ObjectAid UML Explorer Class Diagram | ObjectAid UML Explorer | ObjectAid |
| .UDD | Oleh Yuschuk | File sviluppatore | OllyDbg Module Information | OllyDbg | Oleh Yuschuk |
| .UDF | Open Source | File sviluppatore | Universal Disk Format Image File | 7-Zip | Igor Pavlov |
| .UI | Digia Oyj | File sviluppatore | User Interface File | Qt SDK | The Qt Company |
| .UIH | Geoworks Ensemble | File sviluppatore | Geoworks UI Compiler Espire Header | GEOS | GEOS |
| .UML | Visual Object Modelers | File sviluppatore | UML Data Object Model | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .UMLCLASS | The Eclipse Foundation | File sviluppatore | UML Class Model | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .UNX | Unknown Developer | File sviluppatore | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .USE | Unknown Developer | File sviluppatore | Log File | Microsoft Notepad | Microsoft Corporation |
| .USI | Sublime HQ Pty Ltd | File sviluppatore | UsiXML UI Description Data | Sublime Text | Sublime HQ Pty Ltd |
| .V | Microsoft Corporation | File sviluppatore | Subsampled Raw YUV Image | Microsoft Windows Media Player | Microsoft Corporation |
| .V2X | Texas Instruments, Inc. | File sviluppatore | TI Voyage 200 Macro | TI Connect | Texas Instruments, Inc. |
| .VAC | Ipswitch, Inc. | File sviluppatore | IMail Server Vacation Message File | Ipswitch IMail Server | Ipswitch, Inc. |
| .VAM | Microsoft Corporation | File sviluppatore | Visual Studio Common Tools Vanalyzer Project Item | Microsoft Visual Studio | Microsoft Corporation |
| .VAP | Dialogic | File sviluppatore | Dialogic Indexed Voice Audio File | Syntellect VoiceXML Studio | Syntellect |
| .VAR | M:Pact Technologies | File sviluppatore | Variable Data | My Personal Programmer | M:Pact Technologies |
| .VB | Microsoft Corporation | File sviluppatore | Visual Basic Project Item File | Microsoft Notepad | Microsoft Corporation |
| .VBA | Microsoft Corporation | File sviluppatore | Visual Basic For Applications Project | Microsoft Visual Studio | Microsoft Corporation |
| .VBI | IntelliCAD Technology Consortium | File sviluppatore | IntelliCAD VBA Script | IntelliCAD | IntelliCAD Technology Consortium |
| .VBP | Microsoft Corporation | File sviluppatore | Visual Basic Project File | Microsoft Visual Studio | Microsoft Corporation |
| .VBPROJ.USER | Microsoft Corporation | File sviluppatore | Microsoft Visual Studio Visual Basic Project User Options File | Microsoft Visual Studio | Microsoft Corporation |
| .VBR | Microsoft Corporation | File sviluppatore | Visual Basic Remote Automation Registration | Microsoft Visual Basic | Microsoft Corporation |
| .VBZ | Microsoft Corporation | File sviluppatore | Visual Basic Project Template | Microsoft Visual Basic | Microsoft Corporation |
| .VC | Software Arts | File sviluppatore | VisiCalc Spreadsheet | VisiCalc | Software Arts |
| .VC2 | Microsoft Corporation | File sviluppatore | Microsoft Visual C File | Microsoft Visual C++ | Microsoft Corporation |
| .VC4 | Microsoft Corporation | File sviluppatore | Visual C++ 4 File | Notepad++ | Don Ho |
| .VCH | Wholly Genes, Inc. | File sviluppatore | Master Genealogist Genealogy Chart | The Master Genealogist | Wholly Genes, Inc. |
| .VCL | Open Source | File sviluppatore | Varnish Configuation File | Varnish Cache | Open Source |
| .VCP | Microsoft Corporation | File sviluppatore | eMbedded Visual C++ Project File | Microsoft Visual C++ | Microsoft Corporation |
| .VCPROJ | Microsoft Corporation | File sviluppatore | Visual C++ Project File | Microsoft Visual Studio | Microsoft Corporation |
| .VCX | H+H Software GmbH | File sviluppatore | Virtual Disc Definition File | H+H Software Virtual CD | H+H Software GmbH |
| .VCXPROJ | Microsoft Corporation | File sviluppatore | Microsoft Visual Studio Visual C++ Project | Microsoft Visual Studio | Microsoft Corporation |
| .VDM | Overture Tool | File sviluppatore | VDM Specification File | VDM Tools | Overture Tool |
| .VDP | Microsoft Corporation | File sviluppatore | Visual Studio Deployment Project | Microsoft Visual Studio | Microsoft Corporation |
| .VDPROJ | Microsoft Corporation | File sviluppatore | Visual Studio Setup And Deployment Project | Microsoft Visual Studio | Microsoft Corporation |
| .VDT | General Electric Company | File sviluppatore | VersaPro Variable Declaration Table | VersaPro | General Electric Company |
| .VGC | ViziGen Ltd | File sviluppatore | ViziGen Code Generation Template | ViziGen | ViziGen Ltd |
| .VHD | Microsoft Corporation | File sviluppatore | VHDL Source File | Microsoft Notepad | Microsoft Corporation |
| .VHDL | Microsoft Corporation | File sviluppatore | VHDL Source File | Microsoft Notepad | Microsoft Corporation |
| .VIC | ViziGen Ltd | File sviluppatore | ViziGen Code Import Mappings File | ViziGen | ViziGen Ltd |
| .VIP | JKI | File sviluppatore | Virtual Instrument Package | JKI VIPM | JKI |
| .VIX | EditShare | File sviluppatore | Lightworks Video Index File | Lightworks | EditShare |
| .VJL | Microsoft Corporation | File sviluppatore | Visual J# Source Code | Visual J# | Microsoft Corporation |
| .VM | Apache HTTP Project Management Committee | File sviluppatore | Velocity Template | Apache Velocity | Open Source |
| .VOF | VZ Corporation | File sviluppatore | VZ Programmer Object Folder | VZ Programmer | VZ Corporation |
| .VPC | ViziGen Ltd | File sviluppatore | ViziGen Configuration File | ViziGen | ViziGen Ltd |
| .VPI | Open Source | File sviluppatore | Virtual Pascal OS/2 Unit File | Virtual Pascal | Allan Mertner |
| .VPW | Wheat Stone | File sviluppatore | VoxPro Database File | VoxPro | Wheat Stone |
| .VSCT | Microsoft Corporation | File sviluppatore | Visual Studio Command Table | Microsoft Visual Studio | Microsoft Corporation |
| .VSIXMANIFEST | Microsoft Corporation | File sviluppatore | VSIX Manifest | Microsoft Visual Studio | Microsoft Corporation |
| .VSK | Microsoft Corporation | File sviluppatore | Microsoft Development Common IDE File | Visual Studio IDE | Microsoft Corporation |
| .VSMACROS | Microsoft Corporation | File sviluppatore | Visual Studio Binary Macro Project | Microsoft Visual Studio | Microsoft Corporation |
| .VSMPROJ | Microsoft Corporation | File sviluppatore | Visual Studio Text Macro Project | Microsoft Visual Studio | Microsoft Corporation |
| .VSP | Corel | File sviluppatore | VideoStudio Project File | Corel VideoStudio Pro | Corel |
| .VSPS | Microsoft Corporation | File sviluppatore | Visual Studio Serialized Performance | Microsoft Visual Studio | Microsoft Corporation |
| .VSPX | Microsoft Corporation | File sviluppatore | Visual Studio Performance Report File | Microsoft Visual Studio | Microsoft Corporation |
| .VSSSCC | Microsoft Corporation | File sviluppatore | Visual Studio Solution Source Control File | Microsoft Visual Studio | Microsoft Corporation |
| .VSZ | Microsoft Corporation | File sviluppatore | Visual Studio Wizard File | Microsoft Visual Studio | Microsoft Corporation |
| .VTM | Adobe Systems Incorporated | File sviluppatore | Visual Tool Markup Language Document | Adobe Dreamweaver | Adobe Systems Incorporated |
| .VU | Sony | File sviluppatore | Playstation 2 VU Development Source Code | PlayStation 2 | Sony |
| .VUP | Microsoft Corporation | File sviluppatore | Microsoft Visual Studio Visual C++ Utility Project File | Microsoft Visual Studio | Microsoft Corporation |
| .VWL | PTC | File sviluppatore | Vuforia Word List | PTC Vuforia | PTC |
| .W | Progress Software Corporation | File sviluppatore | OpenEdge Architect Source Code File | OpenEdge | Progress Software Corporation |
| .W3 | APL2000 | File sviluppatore | APL+Win Workspace File | APL+Win | APL2000 |
| .W32 | Microsoft Corporation | File sviluppatore | Win32 Makefile | GNU Make | GNU Operating System |
| .WAM | Team17 | File sviluppatore | Worms Armageddon Mission File | Worms Armageddon | Team17 |
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