| .TLS | AVG Technologies | Uncommon Files | TuneUp Utilities Logon Screen | AVG TuneUp - Unlimited | AVG Technologies |
| .TMB | ARRIS | Uncommon Files | Timbuktu Pro Connection Document | Timbuktu | ARRIS |
| .TML | Odetics Broadcast | Uncommon Files | AIRO Timeline File Format | AIRO | Odetics Broadcast |
| .TMO | Yu Higuchi | Uncommon Files | 3DCG Animation And Pose File | MikuMikuDance | Yu Higuchi |
| .TMPL | Xfire, Inc. | Uncommon Files | Xfire User Interface Template | Xfire | Xfire, Inc. |
| .TNEF | Microsoft Corporation | Uncommon Files | Transport Neutral Encapsulation Format | Microsoft Outlook Express | Microsoft Corporation |
| .TOAD | Unknown Developer | Uncommon Files | FunkyToad System File | FunkyToad Network | Unknown Developer |
| .TOC | Sony | Uncommon Files | Sony PlayStation Portable (PSP) Audio File | Exact Audio Copy for PSP Edition | Interscape |
| .TOO | DigiSoft Innovations | Uncommon Files | Asm Objasm File | Golden Orchard | DigiSoft Innovations |
| .TORRENT | BitTorrent | Uncommon Files | BitTorrent Information File | Shareaza | Open Source |
| .TR1 | IBM | Uncommon Files | IBM Voice Type Languages Addword File | IBM Voice Type | IBM |
| .TRACE | VMware | Uncommon Files | VMware ThinApp Trace Log File | VMware ThinApp 5 Suite | VMware |
| .TRANSFERIR | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .TRY | Microsoft Corporation | Uncommon Files | SCCM 2012 R2 Despoolr.box | Microsoft system center configuration manager | Microsoft Corporation |
| .TSA | Symantec Corporation | Uncommon Files | Jnana.tsa Malware | Avast Antivirus | Avast Software |
| .TSK | Microsoft Corporation | Uncommon Files | Pocket PC Skin | Microsoft ActiveSync | Microsoft Corporation |
| .TSTREAM | Open Source | Uncommon Files | SwarmPlayer Streaming Torrent | SwarmPlayer | Open Source |
| .TTI | Delphi Softwares | Uncommon Files | Trojan File | Beast (Trojan Horse) | Delphi Softwares |
| .TTO | Unknown Developer | Uncommon Files | Client Access Data Specification File | Unknown Software | Unknown Developer |
| .TTX | Simple DirectMedia Layer (SDL) | Uncommon Files | Trados TagEditor File | SDL Trados | SDL Trados |
| .TVLINK | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .TVT | IBM | Uncommon Files | IBM Lenovo ThinkVantage Rescue And Recovery Data File | ThinkVantage Rescue and Recovery | IBM |
| .TVW | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .TVX | Doug Cutting | Uncommon Files | Apache Lucene Term Vector Index File | Apache Lucene | Apache Software Foundation |
| .TVZ | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .TWK | FileMaker Inc. | Uncommon Files | T-Works Manager Data File | T-Works Manager | FileMaker Inc. |
| .TWR | Tripwire, Inc. | Uncommon Files | Tripwire Report File | Tripwire Enterprise | Tripwire, Inc. |
| .TX2 | Typequick Pty Ltd | Uncommon Files | Typequick File | Typequick | Typequick Pty Ltd |
| .TXG | ESRI | Uncommon Files | Georeference Subobject File | ERDAS Imagine | Hexagon Geospatial |
| .TXM | CFP Software Limited | Uncommon Files | CFPwinMan Document File | CFPwinMan | CFP Software Limited |
| .TXS | Delphi Softwares | Uncommon Files | Beast (Trojan Horse) Data File | Beast (Trojan Horse) | Delphi Softwares |
| .TX_ | Microsoft Corporation | Uncommon Files | Compressed TXT File | Microsoft Makecab | Microsoft Corporation |
| .TY2 | Unknown Developer | Uncommon Files | Gualtieri Theme Maker File | Gualtieri Theme Maker | Unknown Developer |
| .TYP | Unknown Developer | Uncommon Files | Thumbs32 File | Unknown Software | Unknown Developer |
| .TZD | AOL | Uncommon Files | Netscape Communicator Locale File | Netscape Communicator | NetScape |
| .TZG | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .U2C | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .U2E | Unreal Software | Uncommon Files | Unreal Game Translation | Unknown Software | Unknown Developer |
| .UAD | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .UBM | Apple | Uncommon Files | IPhoto Mtwain Install File | Apple iPhoto | Apple |
| .UBS | Microsoft Corporation | Uncommon Files | Tracesrv Bugslayer Utility File | Tracesrv Bugslayer Windows Utility Software | Microsoft Corporation |
| .UCA | Unknown Developer | Uncommon Files | Unicode Collation Algorithm Data File | Unknown Software | Unknown Developer |
| .UDI | Pinnacle Systems Inc. | Uncommon Files | Dazzle DVD Complete File | Dazzle DVD Complete | Pinnacle Systems Inc. |
| .UHS | Jason Strautman | Uncommon Files | Universal Hint System Binary Data File | Universal Hint System | Jason Strautman |
| .UK_ | Unknown Developer | Uncommon Files | Mcguiness File | Unknown Software | Unknown Developer |
| .UNIX BAR COMPRESSED FILE ARCHIVE | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .UNKNOWN | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .UNL | Garmin | Uncommon Files | Garmin Unlock File | MapSource | Garmin |
| .UNM | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .UP2 | Ulead Systems | Uncommon Files | Ulead Cool 3D Plugins Board File | MotionStudio 3D | Corel |
| .UPDATED | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .UPG | Unknown Developer | Uncommon Files | Upgrade File | ANCILE uPerform Client | ANCILE Solutions |
| .USAGE | Unknown Developer | Uncommon Files | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .USB | SiSoftware | Uncommon Files | SiSoftware Sandra Data | SiSoftware Sandra | SiSoftware |
| .UVC | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .UXR | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .UXT | WaveMetrics | Uncommon Files | IGOR Pro Unpacked Experiment Template File | IGOR Pro | WaveMetrics |
| .V11 | bexio AG | Uncommon Files | ESR V11 Data | Einzahlungsschein mit Referenznummer (ESR) | bexio AG |
| .V48 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .V50 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .VAX | Unknown Developer | Uncommon Files | Pbm Plus File | Unknown Software | Unknown Developer |
| .VCB | VMware | Uncommon Files | VMware Consolidated Backup Archive | VMware Server | VMware |
| .VCMP | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VCY | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VC_ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VDH | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VDI | Oracle Corporation | Uncommon Files | VirtualBox Virtual Disk Image | Oracle VM VirtualBox | Oracle Corporation |
| .VDMPVF | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VHA | Macromedia | Uncommon Files | Macromedia Sitespring File | Unknown Software | Unknown Developer |
| .VHDPMEM | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .VHP | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VIR | Symantec Corporation | Uncommon Files | Virus Infected File | Avira Antivirus Pro 2016 | Avira Operations GmbH & Co. KG. |
| .VKL | Virtualedit | Uncommon Files | Virtual Edit File | Virtual Edit | Virtualedit |
| .VLQ | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VMCZ | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .VMG | Nokia | Uncommon Files | Nokia Text Message | Nokia PC Suite | Nokia |
| .VMSG | VMware | Uncommon Files | VMware Application Message File | VMware Workstation | VMware |
| .VOR | Sun Microsystems | Uncommon Files | StarOffice Template | Apache OpenOffice | Apache Software Foundation |
| .VPA | Halsoft.com, Inc | Uncommon Files | VPchat Chat Gestures File | VPchat | Halsoft.com, Inc |
| .VPH | optikVerve Labs | Uncommon Files | VirtualPhotographer Custom Settings | Adobe Photoshop | Adobe Systems Incorporated |
| .VRA | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VS | OpenGL | Uncommon Files | Vertex Shader File | Microsoft DirectX SDK | Microsoft Corporation |
| .VSTEMPLATE | Microsoft Corporation | Uncommon Files | Microsoft Visual Studio Project Template | Microsoft Visual Studio | Microsoft Corporation |
| .VUX | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .VYB | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .W | Progress Software Corporation | Uncommon Files | OpenEdge Architect Source Code File | OpenEdge | Progress Software Corporation |
| .W2F | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .W73 | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WAL | Nullsoft | Uncommon Files | Winamp Modern Skin | Nullsoft Winamp | Nullsoft |
| .WBA | Stardock Corporation | Uncommon Files | WindowBlinds Compressed Skin | WindowBlinds | Stardock Corporation |
| .WC4 | Unknown Developer | Uncommon Files | WinCheckIt4 Settings File | Unknown Software | Unknown Developer |
| .WCINV | Microsoft Corporation | Uncommon Files | Windows Meeting Space Invitation File | Windows Meeting Space | Microsoft Corporation |
| .WCM | Corel | Uncommon Files | WordPerfect Macro | Corel WordPerfect X8 | Corel |
| .WCXF | PenPower | Uncommon Files | WorldCard Exchange File | WorldCard Mobile | PenPower |
| .WDSEML | Mozilla | Uncommon Files | Thunderbird Searchable Email File | Mozilla Thunderbird | Mozilla |
| .WEBARCHIV | Unknown Developer | Uncommon Files | Unknown File Type | Unknown Software | Unknown Developer |
| .WEI | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .WER | Microsoft Corporation | Uncommon Files | Windows Error Report File | Microsoft Notepad | Microsoft Corporation |
| .WF2 | Unknown Developer | Uncommon Files | Uncommon File Extension | Unknown Software | Unknown Developer |
| .WGS | ChannelAdvisor | Uncommon Files | Walk-Graph Segment File | RichFX Player | eHelp Corporation |
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