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