| 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 |
| llge | Microsoft Windows Application Log |
| lli | Autodesk AutoCAD Landscape Library |
| llk | TreeMix Likelihood Data |
| lll | Light LossLess Compressed 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 |
| lmat | LayaAir Material Data |
| lmbs | Adobe Photoshop for Mac Filter |
| lmc | Library Manager Database |
| lmd | Abbyy FineReader Morphological Model |
| lmf | Altera Library Mapping File |
| lmf-ms | Microsoft Office Live Meeting Settings Data |
| lmg | CryENGINE Locomotion Manager Group Animation |
| lmh | Memory Hacking Software LMH Data |