| lss | LotusScript Source Code |
| lst | GCC Assembler Listing File |
| lst | IAR System List Output Data |
| lst | µVision Assembler Listing Data |
| ltb | LithTech Binary File |
| lua | LUA Source Code |
| luac | LUA Compiled Source Code |
| lub | LUA Binary |
| luc | LuaTeX Compiled LUA Script |
| luca | Luca Template |
| luci | LuCI Script |
| lucidsnippet | Lucid Snippet Data |
| lvlad | LabVIEW Ladder Diagram |
| lvm | LabVIEW Measurement |
| lvr | Microsoft Test Manager Link |
| lxb | LXBatch Program |
| lxp | LXP Source Code |
| m | MATLAB Script |
| m1s | Mach3 Macro |
| m2o | Modula Fitted Modula2 Data |
| m2o | MSSQL-to-Oracle Profile Description Data |
| m3 | Modula-3 Source Code |
| m4 | M4 Macro File |
| m4m | SynDEx Makefile Macro |
| m4x | SynDEx Executive Macro |
| m51 | µVision Listing Data |
| m66 | µVision Listing Data |
| m6m | Mazatrol M640M NC Unit |
| mac | IAR System C-SPY Macro Definition Data |
| mac | UltraEdit Macro |
| magik | Magik Source Code |
| mak | Visual Studio Makefile |
| make | Xcode Make File |
| mako | Mako Template |
| mal | Yaskawa MPE720 v5 Application |
