| .L4D | MAXON Computer | Innstillingsfiler | Cinema 4D Layout File | MAXON Cinema 4D | MAXON Computer |
| .L64 | Commodore International | Innstillingsfiler | 64LAN Image File | Unknown Software | Unknown Developer |
| .LANG | Mojang | Innstillingsfiler | Minecraft Language File | Microsoft Notepad | Microsoft Corporation |
| .LAUNCH | Rogue Wave | Innstillingsfiler | Zend Studio Debugger Configuration Data | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .LAY | Tecplot, Inc | Innstillingsfiler | Tecplot Layout File | Tecplot 360 | Tecplot, Inc |
| .LAYOUT | Apple | Innstillingsfiler | Apple MainStage Layout Data | Logic Studio | Apple |
| .LBU | Interscape | Innstillingsfiler | Cloaked Affiliate Link Builder Settings File | Cloaked Affiliate Link Builder | Interscape |
| .LCC | IBM | Innstillingsfiler | IBM Voice Type Languages Newuser File | IBM Voice Type | IBM |
| .LED | Sony | Innstillingsfiler | Sony AIBO LED Lights Control Data | Unknown Software | Unknown Developer |
| .LENS | Autodesk, Inc. | Innstillingsfiler | Autodesk Stitcher Camera Profile | Autodesk Stitcher Unlimited | Autodesk, Inc. |
| .LES | David A. Wheeler | Innstillingsfiler | Lesson File | Mklesson | David A. Wheeler |
| .LF | Concept Software | Innstillingsfiler | SoftwareKey License | Protection PLUS | Concept Software |
| .LGT | Microsoft Corporation | Innstillingsfiler | Let's Go! Theme File | Let's Go! | Microsoft Corporation |
| .LH3D | BeLight Software | Innstillingsfiler | Live Home 3D Project | Live Home 3D | BeLight Software |
| .LIC | Unknown Developer | Innstillingsfiler | Software License File | Microsoft Visual C++ | Microsoft Corporation |
| .LIR | Applied Digital | Innstillingsfiler | ADI Ocelot Settings File | C-Max | Applied Digital |
| .LKF | PCS Systemtechnik GmbH | Innstillingsfiler | INTUS Terminal Keyboard Settings | INTUS 5600 MULTIFUNCTIONAL TERMINAL | PCS Systemtechnik GmbH |
| .LKG | Hewlett-Packard | Innstillingsfiler | HP-UX Configuration Data | HP-UX 11i Web Server Suite | Hewlett-Packard |
| .LLC | LapLink Software | Innstillingsfiler | LapLink Saved Connection File | LapLink | LapLink Software |
| .LLP | General Electric Company | Innstillingsfiler | VersaPro Local Logic Block | VersaPro | General Electric Company |
| .LOCAL | Embarcadero Technologies | Innstillingsfiler | Delphi User-Specific Project Options | Delphi (IDE) | Embarcadero Technologies |
| .LOOK | Adobe Systems Incorporated | Innstillingsfiler | SpeedGrade Look File | Adobe SpeedGrade | Adobe Systems Incorporated |
| .LOP | ValuSoft | Innstillingsfiler | MasterCook Layout File | ValuSoft MasterCook | ValuSoft |
| .LSV | Light-O-Rama | Innstillingsfiler | Light-O-Rama Sequence Editor Visual Preference File | Light-O-Rama | Light-O-Rama |
| .LSW | Technics | Innstillingsfiler | Technics Keyboard Current Panel File | Unknown Software | Unknown Developer |
| .LT | Andrew Jewett | Innstillingsfiler | Moltemplate Data File | Moltemplate | Andrew Jewett |
| .LVA | Logitech | Innstillingsfiler | Logitech Video Effects Avatar File | Logitech Webcam Software | Logitech |
| .LVF | Logitech | Innstillingsfiler | Logitech Video Effects File | Logitech Webcam Software | Logitech |
| .LVT | Open Source | Innstillingsfiler | Land Surface Verification Toolkit Configuration | Land Information System Verification Toolkit (LVT) | Open Source |
| .LWL | Johm Mackernon Software | Innstillingsfiler | Lightwright Printed Paperwork Formatting Instructions Data | LightWright | Johm Mackernon Software |
| .LX | IBM | Innstillingsfiler | LPEX Customization Command Profile File | LPX Editor | IBM |
| .LYT | Adminsoft | Innstillingsfiler | Adminsoft Document Layout File | Adminsoft | Adminsoft |
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