| 1 | L | Mike Lesk | Lex Source Format |
| 2 | LA | La | Lossless Audio Format |
| 3 | LAB | Corel | WordPerfect Label Definition Format |
| 4 | LABELS | N/A | Amira 3D mesh related data |
| 5 | LACCDB | Microsoft | Microsoft Access Lock Format |
|
| 6 | LANG | Skype Software | Skype Language Settings Format |
| 7 | LAP | N/A | Generic |
| 8 | LAS | ASPRS | LIDAR Data Exchange Format |
| 9 | LASSO | LassoSoft | Lasso Database-Driven Web Page |
| 10 | LATEX | N/A | LaTeX Document |
| 11 | LAUNCH | Zend Technologies Ltd. | Zend Studio Debugger Configuration |
| 12 | LAYOUT | Apple | Apple MainStage Layout Format |
| 13 | LBF | 2K Games | Bioshock 2 Configuration |
| 14 | LBM | Electronic Arts | Deluxe Paint Bitmap Image |
| 15 | LBX | Microsoft | FoxPro Label Format |
| 16 | LCF | Graphisoft | ArchiCAD Library Container Format |
| 17 | LCK | N/A | Program Lock Format |
| 18 | LCN | Corel Corporation | Corel WordPerfect Dictionary Format |
| 19 | LCPP | N/A | Adobe Lens Profile Creator project |
| 20 | LCX | Cray Inc. | LC Model |
| 21 | LD2 | Lingoes Project | Lingoes Dictionary Format |
| 22 | LDB | Microsoft | Microsoft Access Lock Format |
| 23 | LDF | Microsoft | SQL Server Transaction Log Format |
| 24 | LDIF | N/A | LDAP Data Interchange Format |
| 25 | LDL | Corel Corporation | Corel Paradox Delivered Library |
| 26 | LEF | N/A | LEN Exchange Format |
| 27 | LEPF | N/A | Adobe Little Endian Prebuilt Format |
| 28 | LESS | Alexis Sellier | LESS Style Sheet |
| 29 | LEX | Adobe Systems | Adobe Linguistic Library Data Format |
| 30 | LFP | IPRO Tech | IPRO LFP Format |
| 31 | LFS | Samsung | Samsung Phone Params.lfs Format |
| 32 | LGE | N/A | Generic |
| 33 | LGM | Microsoft Corporation | Microsoft Windows Application Log |
| 34 | LGZ | Microsoft Corporation | Windows Application Log |
| 35 | LHA | N/A | LHARC Compressed Archive |
| 36 | LHARC | Ivan Zahariev | LH ARC Compressed Archive |
| 37 | LHR | Intuit | Quicken Financial Life For Mac Format |
| 38 | LHS | N/A | Literate Haskell Script |
| 39 | LHZ | N/A | LHA Compressed Format Archive |
| 40 | LIBRARY-MS | Microsoft | Windows Library Description Format |
| 41 | LIC | N/A | Software License Format |
| 42 | LICKEY | Online Media Technologies Ltd. | AVS4YOU License Key |
| 43 | LID | Intuit Inc. | Quicken 2002 Deluxe Format |
| 44 | LIF | Leica Microsystems | Leica Image Format |
| 45 | LIK | N/A | Trojan.Win32.Agent.lik |
| 46 | LIN | Autodesk | AutoCAD Linetype Format |
| 47 | LINUX | Various Linux developers | Linux |
| 48 | LIS | N/A | SQR Output Format |
| 49 | LISP | N/A | Lisp Source Code Format |
| 50 | LIST | Oracle | JAR Index Format |
| 51 | LIT | Microsoft | EBook Format |
| 52 | LITCOFFEE | N/A | Literate CoffeeScript source code |
| 53 | LK# | N/A | Autodesk multi-user coordination lock data |
| 54 | LKH | N/A | Worm.Generic.LKH Virus |
| 55 | LM | Microsoft | Language Model File |
| 56 | LMG | CRYTEK | CryENGINE Locomotion Group Animation |
| 57 | LMX | Nokia | Landmark Exchange Format |
| 58 | LN | IBM | UNIX Lint |
| 59 | LNC | Sports Interactive | Football Manager Player |
| 60 | LNG | Nullsoft | Language Application Support Format |
| 61 | LNK | Microsoft | Windows Format Shortcut |
| 62 | LNM | Corel Corporation | Corel WordPerfect SGML Alias |
| 63 | LNS | AVG Technologies (Grisoft) | AVG Anti-Virus Language |
| 64 | LNST | Adobe Systems | Adobe InDesign Line Presets Format |
| 65 | LNT | Gimpel Software | PC-lint/FlexeLint Configuration Format |
| 66 | LOADED_0 | N/A | Generic |
| 67 | LOADED_1 | N/A | JavaScript cache file |
| 68 | LOADED_2 | N/A | JavaScript cache |
| 69 | LOADED_3 | N/A | JavaScript cache |
| 70 | LOB | IBM | IBM DB2 LOBFILE |
| 71 | LOC | N/A | GPS Location Format |
| 72 | LOCALIZED | Apple, Inc. | MAC OS X |
| 73 | LOCALSTORAGE | The WebKit Open Source Project | WebKit Local Storage Data Format |
| 74 | LOCALSTORAGE-JOURNAL | Google Inc. | Google Chrome Rollback Journal |
| 75 | LOCATION | N/A | Microsoft Windows 10 registry data |
| 76 | LOCK | N/A | Lock Format |
| 77 | LOCKED | N/A | Ransomware Encrypted File |
| 78 | LOCK_SYNC | Apple, Inc. | Synchronization Lock |
| 79 | LOG | N/A | Log Format |
| 80 | LOGIC | Apple | Logic Pro Project Format |
| 81 | LOGIN | The Open Group | UNIX Command |
| 82 | LOGONXP | Stardock | LogonStudio Windows XP Logon Screen |
| 83 | LOL | Adam Lindsay | LOLCODE Source Code FIle |
| 84 | LOLS | N/A | LOLCODE Source Code |
| 85 | LP | Autodesk | Lightscape Preparation Format |
| 86 | LPROJ | N/A | Localized Project Folder |
| 87 | LRC | N/A | Lyrics Format |
| 88 | LRF | Sony | Sony Portable Reader Format |
| 89 | LRN | Apple, Inc. | Apple Chess User Data |
| 90 | LRS | N/A | Librie Reader Source Format |
| 91 | LRV | GoPro | Low Resolution Video Format |
| 92 | LSL | Corel Corporation | Corel Paradox Format |
| 93 | LSM | Carl Zeiss AG | Ziess LSM Model |
| 94 | LSO | Apple | Logic Audio Project |
| 95 | LSP | N/A | Lisp Program Source Code Format |
| 96 | LSS | IBM | LotusScript Source Code |
| 97 | LST | N/A | Data List |
| 98 | LSTX | Rick Meyers | E-Sword Verse List |
| 99 | LT2 | Smith Micro | Poser Light Set Format |
| 100 | LTA | Monolith Productions, Inc. | Monolith Lithtech Game Engine |
| 101 | LTL | DIAL GMBH | DIALux Luminaire Data |
| 102 | LTR | N/A | Letter Format |
| 103 | LTT | N/A | HP Library And Tape Tools Log |
| 104 | LTZ | Smith Micro | Compressed Poser Light Set Format |
| 105 | LUA | PUC-Rio | Lua Source Format |
| 106 | LUE | Symantec | Norton LiveUpdate Log Format |
| 107 | LUG | N/A | Game |
| 108 | LUV | Sega Corporation | Medieval 2 Total War |
| 109 | LVL | N/A | Game Level Format |
| 110 | LVM | National Instruments | LabVIEW Measurement Format |
| 111 | LWF | N/A | LuraWave Format Image Format |
| 112 | LWG | N/A | Microsoft .NET data |
| 113 | LWO | NewTek | LightWave 3D Object Format |
| 114 | LWOB | NewTek, Inc. | LightWave 3D Object |
| 115 | LWP | IBM | Lotus Word Pro Document |
| 116 | LWS | NewTek | LightWave 3D Scene Format |
| 117 | LXF | LEGO | LEGO Digital Designer Model Format |
| 118 | LXFML | LEGO | LEGO Digital Designer XML Format |
| 119 | LXO | Luxology | Luxology Modo 3D Image |
| 120 | LY | GNU | LilyPond Format |
| 121 | LZC | Electronic Arts, Inc. | Need For Speed Undercover Game Data |
| 122 | LZH | N/A | LZH Compressed Format |
| 123 | LZMA | N/A | LZMA Compressed Format |
| 124 | LZO | N/A | LZO Compressed Format |
| 125 | LZP | Legacy Interactive | Law And Order 3: Justice Is Served Game |
| 126 | LZX | N/A | Amiga LZX Compressed Format |
