| lanalyser | Novell Netware LANalyzer Trace Data |
| land | Userland Frontier Data |
| lang | Skype Language File |
| langz | DigiChat Language Data |
| lar | Liquid Audio Player Registration Data |
| las | Lidar Data Exchange Format File |
| las | Log ASCII Standard |
| lat | Crossword Express Lattice Data |
| lau | AutoClient Local Authentication Data |
| lav | Liquid Audio Player Voucher Data |
| lavs | Liquid Audio Player Secured Download Data |
| lax | AnetHelpTool JavaHelp Viewer File |
| lay | Pro/ENGINEER Layout |
| lay | ArchiCAD PlotMaker Layout |
| lay | Lightscape Layer File |
| lay | Rhino 3D Layer |
| layout | Adobe Premiere Workspace Layout |
| layx | PTV VISSIM Vehicle Network Data |
| laz | LASzip Compressed Lidar Data |
| lbd | Life Balance Data File |
| lbe | Life Balance XML Exchange Data |
| lbg | dBASE IV Label Generator Data |
| lbk | ArchiCAD PlotMaker Layout Book |
| lbo | dBASE IV Compiled Label |
| lbr | EAGLE Library File |
| lbv | T-Online Ob4hbci Layout Print File |
| lbxcol | Libronix DLS Resource Collection |
| lbxdtp | Libronix DLS Data Type |
| lbxlls | Logos 3 LLS Data |
| lbxoeb | Libronix DLS Resource |
| lby | Oracle Documaker Library Data |
| lc | L0phtCrack Password Database |
| lcb | Kodak EasyShare Album List |
| lcd | Abbyy FineReader Dictionary File |
| lcf | ArchiCAD Library Container File |