| lbr | Omnis Library |
| lbs | Omnis Application Library |
| lbt | Visual FoxPro Label Memo |
| lbx | Visual FoxPro Label |
| lc | LiveCode Script |
| lc3 | LC-3 Assembly Source Code |
| lc463 | LiveCode Script |
| lc464 | LiveCode Script |
| ldf | ProWorx NXT Logic Data File |
| ldml | Lasso Dynamic Markup Language Document |
| lds | Binutils Linker Script |
| lds | Liquid Studio Source Code |
| ldx | Liquid Studio Compiled Executable |
| less | LESS Style Sheet |
| lfm | Lazarus Form |
| lg32 | GFA-BASIC 32 Library |
| lgf | ProWorx NXT Log Book Note |
| lgo | Logo Source Code |
| lgt | Logtalk Source Code |
| lhs | Literate Haskell Script |
| lib | ESPL Encrypted Programming File |
| lib | Visual C++ Import Library |
| license | Visual Studio Binary License Data |
| licx | Visual Studio License Text |
| lif | HP-UX LIF File |
| lin | µVision Linker Control Data |
| link | Eclipse Link File |
| linq | LINQPad Source Code |
| lipg | LiPG Parser |
| lis | HP OpenVMS List Data |
| lisp | Lisp Source Code |
| litcoffee | CoffeeScript Literate Script |
| livecode | LiveCode Stack File |
| lkc | LTIB Top Level Config |
| lkf | Code Composer Studio Linker Options Data |
