| .LLB | National Instruments | Arquivos de dados | LabVIEW Library File | LabVIEW | National Instruments |
| .LLF | Unknown Developer | Arquivos de dados | IITM Local Language Data | IITM | Unknown Developer |
| .LLV | Locklizard | Arquivos de dados | Lizard Safeguard License | Lizard Safeguard PDF Security | Locklizard |
| .LMD | ABBYY | Arquivos de dados | Abbyy Finereader Sprint File | ABBYY FineReader | ABBYY |
| .LMH | Open Source | Arquivos de dados | Memory Hacking Software Memory File | Memory Hacking Software | Open Source |
| .LMR | Intuit, Inc. | Arquivos de dados | QuickBooks Loan Manager Data | QuickBooks | Intuit, Inc. |
| .LMT | ENTERBRAIN, INC. | Arquivos de dados | RPG Maker 2000/2003 Map Tree | RPG Maker VX | ENTERBRAIN, INC. |
| .LMX | Nokia | Arquivos de dados | Landmark Exchange File | Nokia PC Suite | Nokia |
| .LNB | Mike Bradley | Arquivos de dados | Logomanager File | LogoManager | Mike Bradley |
| .LNF | Open Source | Arquivos de dados | Oyoaha Lookandfeel Interface Elements File | oyoaha lookandfeel | Open Source |
| .LNG | Nullsoft | Arquivos de dados | Winamp Language File | Nullsoft Winamp | Nullsoft |
| .LNGX | Dominik Reichl | Arquivos de dados | KeePaas Language Data | KeePass Password Safe | Open Source |
| .LNM | Corel | Arquivos de dados | Corel WordPerfect SGML Alias File | Corel WordPerfect | Corel |
| .LNS | AVG Technologies | Arquivos de dados | AVG Anti-Virus Language Data File | AVG Antivirus | AVG Technologies |
| .LNT | Gimpel Software | Arquivos de dados | PC-lint/FlexeLint Configuration File | Microsoft Notepad | Microsoft Corporation |
| .LOAD | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LOADER | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LOAN | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LOC | TopoGrafix | Arquivos de dados | GPS Location File | EasyGPS | TopoGrafix |
| .LOCAL | Embarcadero Technologies | Arquivos de dados | Delphi User-Specific Project Options | Delphi (IDE) | Embarcadero Technologies |
| .LOCALSTORAGE | Google | Arquivos de dados | WebKit Local Storage Data File | Google Chrome | Google |
| .LOG | Unknown Developer | Arquivos de dados | Log File | Microsoft Notepad | Microsoft Corporation |
| .LOGO | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LOGON | Unknown Developer | Arquivos de dados | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .LOT | Leslie Lamport | Arquivos de dados | LaTeX List Of Tables | LaTex | Leslie Lamport |
| .LP1 | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
| .LP7 | Lex Persona | Arquivos de dados | LP7 Digital Signed File | LP7Creator | Lex Persona |
| .LPA | MP Filtri | Arquivos de dados | LPA View Laser Particle Analyser Data | LPA View | MP Filtri |
| .LPD | GNU Project | Arquivos de dados | LPD Daemon Print Permissions File | Vim | Bram Moolenaar |
| .LPF | Orgadata AG | Arquivos de dados | Orgadata LogiKal File | LogiKal | Orgadata AG |
| .LPI | Unknown Developer | Arquivos de dados | Laser Printer Information | Unknown Software | Unknown Developer |
| .LPJ | Interscape | Arquivos de dados | LIMDEP Project | LIMDEP | Interscape |
| .LPK | ESRI | Arquivos de dados | ArcGIS Layer Package | ESRI ArcGIS for Desktop | ESRI (Environmental Systems Research Institute) |
| .LPN | n.v. Systems Europe s.a. | Arquivos de dados | LVPLAN Data | LVPLAN | n.v. Systems Europe s.a. |
| .LPP | CyberLink | Arquivos de dados | LabelPrint Project File | CyberLink LabelPrint 2.5 | CyberLink |
| .LPS | DAZ 3D | Arquivos de dados | Bryce Leaf Shape File | DAZ 3D Bryce | DAZ 3D |
| .LPT | Interscape | Arquivos de dados | LogPlot Compiled Boring Log File | LogPlot | Interscape |
| .LQ | Unknown Developer | Arquivos de dados | Unknown Apple II File. (found On Golden Orchard Apple II CD Rom) | Atom | GitHub, Inc. |
| .LQA | Vernier Software & Technology | Arquivos de dados | Logger Pro Automatic Update | Vernier Logger Pro | Vernier Software & Technology |
| .LQF | Open Source | Arquivos de dados | LeechFTP Saved Queue | LeechFTP | Open Source |
| .LQM | LG Electronics | Arquivos de dados | LG QuickMemo Note | LG QuickMemo | LG Electronics |
| .LQP | Liquid Audio Inc | Arquivos de dados | Liquid Audio Player Passport Data | Liquid Audio Player | Liquid Audio Inc |
| .LQU | LeapWare | Arquivos de dados | LeapFTP Queue Data | LeapFTP | LeapWare |
| .LR | Adtollo | Arquivos de dados | Chaos Desktop Layer List File | Chaos desktop | Adtollo |
| .LRM | Microsoft Corporation | Arquivos de dados | Encarta Class Server Learning Resource File | Microsoft Encarta | Microsoft Corporation |
| .LRT | Aequus Gaming LTD | Arquivos de dados | League Of Legends Replay File | LOLReplay | Aequus Gaming LTD |
| .LRV | Konica Minolta | Arquivos de dados | Konica Minolta Data Management Software Stored File | Konica Minolta Data Management Software | Konica Minolta |
| .LSD | ENTERBRAIN, INC. | Arquivos de dados | RPG Maker Game Save File | RPG Maker VX | ENTERBRAIN, INC. |
| .LSF | Interscape | Arquivos de dados | Logos Library System File | Logos Bible Software | Interscape |
| .LSI | Hewlett-Packard | Arquivos de dados | Xerox Lightscribe Label | LightScribe Template Labeler | Hewlett-Packard |
| .LSL | Corel | Arquivos de dados | Corel Paradox File | Corel Paradox | Corel |
| .LSP | Open Source | Arquivos de dados | Lisp Program Source Code File | MacroMates TextMate | MacroMates |
| .LSQ | IBM | Arquivos de dados | IBM Voice Type Languages Addword Data | IBM Voice Type | IBM |
| .LSR | SolarWinds Inc. | Arquivos de dados | LANsurveyor Report | LANsurveyor | SolarWinds Inc. |
| .LST | Unknown Developer | Arquivos de dados | Data List | LibreOffice | The Document Foundation |
| .LT | Andrew Jewett | Arquivos de dados | Moltemplate Data File | Moltemplate | Andrew Jewett |
| .LTD | Lifescope Inc | Arquivos de dados | LivingTime Data File | LivingTime | Lifescope Inc |
| .LTM | IBM | Arquivos de dados | IBM Lotus Forms Form | IBM Lotus Forms Viewer | IBM |
| .LTT | Hewlett-Packard | Arquivos de dados | HP Library And Tape Tools Log | Notepad++ | Don Ho |
| .LTX | GSC Game World | Arquivos de dados | S.T.A.L.K.E.R. Properties File | GSC Game World S.T.A.L.K.E.R.: Call of Pripyat | GSC Game World |
| .LUAR | UltraDefrag Development Team | Arquivos de dados | UltraDefrag Lua Report | UltraDefrag | UltraDefrag Development Team |
| .LUB | Interscape | Arquivos de dados | Lua Bytecode | LUA | Interscape |
| .LUCIDCOLORSET | The Escapers | Arquivos de dados | Lucid Color Set File | Lucid | The Escapers |
| .LUCY | HTC | Arquivos de dados | HTC Scribble Note | HTC Scribble | HTC |
| .LUD | ABBYY | Arquivos de dados | Lingvo User Dictionary File | ABBYY Lingvo Dictionary | ABBYY |
| .LUM | Kevin Chong | Arquivos de dados | Luminous Song List | Luminous | Kevin Chong |
| .LUT | Lutron Electronics Co., Inc | Arquivos de dados | RadioRA Essentials Project Database | Lutron Electronics RadioRA Essentials | Lutron Electronics Co., Inc |
| .LVM | National Instruments | Arquivos de dados | LabVIEW Measurement File | LabVIEW | National Instruments |
| .LVS | Daylon Graphics | Arquivos de dados | Daylon Leveller Selection Mask File | Daylon Leveller | Daylon Graphics |
| .LVW | New Wave Concepts | Arquivos de dados | Livewire Document | LiveWire | New Wave Concepts |
| .LW | NewTek | Arquivos de dados | LightWave 3D Binary File | LightWave 3D | NewTek |
| .LW2 | Johm Mackernon Software | Arquivos de dados | Lightwright Version 2 Show Data File | LightWright | Johm Mackernon Software |
| .LW4 | Johm Mackernon Software | Arquivos de dados | Lightwright File | LightWright | Johm Mackernon Software |
| .LW5 | Johm Mackernon Software | Arquivos de dados | Lightwright File | LightWright | Johm Mackernon Software |
| .LWD | EditShare | Arquivos de dados | Lightworks Data File | Lightworks | EditShare |
| .LWO | NewTek | Arquivos de dados | LightWave 3D Object File | Poser | Smith Micro Software |
| .LWP | IBM | Arquivos de dados | Lotus Word Pro Document | IBM Lotus Word Pro | IBM |
| .LWR | Atari Corporation | Arquivos de dados | RollerCoaster Tycoon Laser Writing File | RollerCoaster Tycoon | Chris Sawyer |
| .LXE | Foundry | Arquivos de dados | Luxology Modo Environment Preset | Modo | Foundry |
| .LXF | The LEGO Group | Arquivos de dados | LEGO Digital Designer Model File | LEGO Digital Designer | The LEGO Group |
| .LXK | Open Source | Arquivos de dados | Lexicon Link-up File | COREX | Open Source |
| .LY | GNU Operating System | Arquivos de dados | LilyPond File | LilyPond | GNU Project |
| .LYC | SPGPrints Group | Arquivos de dados | BestIMAGE Compressed Design File | spgprints bestIMAGE | SPGPrints Group |
| .LYT | Adminsoft | Arquivos de dados | Adminsoft Document Layout File | Adminsoft | Adminsoft |
| .LYX | Open Source | Arquivos de dados | XWE File | XWE | Open Source |
| .LZZZZZZZ | Apple | Arquivos de dados | Golden Orchard Apple II CD Rom File | Apple OS X | Apple |
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