| lin | Autodesk AutoCAD Linetypes |
| lin | LISCAD Line Styles Data |
| linf | LinF Source Code |
| link | iPod Link Data |
| linx | iPod Links Folder Data |
| lir | CAP42 License Request File |
| lis | LISREL Syntax Data |
| lis | Tekla Structures Exported Model |
| lis | SQR Printer Output |
| list | PLINK Genotype List File |
| lit | Avantes Avasoft v8 Wavelength Coefficients Data |
| lith | DROPS Simulator Lithology Data |
| little | Mozilla Firefox Start-up Cache |
| liv | Living Actor Data File |
| livereg | Symantec Antivirus Session |
| liveupdate | Symantec LiveUpdate Data |
| lix | ExtendSim Simulation Software Library |
| ljb | LightJockey Database |
| lk | OpenInsight LK Data |
| lka | Lookout Direct Security Data |
| lkb | Faverly Data Recorder 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 |