| list | PLINK Genotype List File |
| listlayout | Adium Contact List Layout |
| listtheme | Adium Contact List Theme |
| lit | Avantes Avasoft v8 Wavelength Coefficients Data |
| litematic | Litematica Data |
| lith | DROPS Simulator Lithology Data |
| little | Mozilla Firefox Start-up Cache |
| liv | Living Actor Data File |
| liveupdate | Symantec LiveUpdate Data |
| lix | ExtendSim Simulation Software Library |
| lix | Logos Library System Book Data |
| ljb | LightJockey Database |
| lk | OpenInsight LK Data |
| lk | Progress OpenEdge Database Lock |
| lka | Lookout Direct Security Data |
| lko | Microsoft Outlook Express Junkmail Data |
| lkp | Microsoft SMS Lookup File |
| lkt | EES Lookup Table |
| lkup | iiV Lookup |
| ll | List and Label Preview |
| ll3 | LapLink 3 Data |
| lla | PROJ.4 LLA Data |
| llc | LapLink Saved Connection Data |
| lld | Loan Level Disclosure Data |
| llge | Microsoft Windows Application Log |
| lli | Autodesk AutoCAD Landscape Library |
| llk | TreeMix Likelihood Data |
| llog | Legit Log Viewer Log Data |
| llt | Liquidity Lighthouse Transaction Data |
| llv | Lizard Safeguard PDF Security License File |
| lm | ARPA-MIT Language Model File |
| lm3 | Bosphorus 3D Landmarking Database |
| lm4 | Steinberg LM-4 Program |
| lma | Logik-Manager Protect Data |
| lmat | LayaAir Material Data |
