| kpz | Komodo IDE Compressed Package |
| kqb | Pyke Knowledge Question Base |
| krb | Pyke Knowledge Rule Base |
| krt | Visual FoxPro KRT File |
| ks | Mer Kickstart File |
| ksh | KSH Shell Script |
| ksql | KSQL Script |
| kss | Kinetic Style Sheet |
| kt | Kotlin Source Code |
| kts | Kotlin Script |
| ktt | Uniface Keyboard Translation Table |
| ktx | OpenGL Texture Data |
| ktx2 | Khronos 2 OpenGL Texture Data |
| kv | Kivy Source Code |
| kvh | Key-Value-Hierarchy Format Data |
| kwf | Delphi Pascal Chart Data |
| kx | KiXtart Tokenized Script |
| kxf | Koda FormDesigner Data |
| kxx | Keyman Developer Encrypted Keyboard File |
| kzb | Kanzi Binary |
| l | Lex Source Code |
| Lisp Source Code |
| Xcode Core Lex Source Code |
| la | GNU Libtool Archive |
| lai | GNU Libtool Temporary Data |
| lamp | ArchiCAD Geometric Description Language Source Code |
| lang | GtkSourceView Language Definition |
| lap | Scheme Source Code |
| layerdiagram | Visual Studio Layer Diagram |
| layout | Code::Blocks Layout File |
| lba | Liberty BASIC Source Code |
| lbb | LB Booster Program |
| lbj | Learning Based Java Source Code |
| lbk | VersaPro Local Logic Block Backup |
| lbl | dBASE IV Label Data |
| lbp | ProWorx NXT Logic Pointer Data |
| lbr | Micro Focus COBOL Data |
| 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 |
| lcf | Norton Guide Linker Control File |
| ld | Binutils Linker Script |
| ldd | Visual Studio Logical Datacenter Diagram Data |
| ldf | ProWorx NXT Logic Data File |
| ldml | Lasso Dynamic Markup Language Document |
| lds | Binutils Linker Script |
| 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 |
| LOGO!Soft Comfort Standard Data |
| MSWLogo Program Design |
| lgt | Logtalk Source Code |
| lhs | Literate Haskell Script |
| lib | ESPL Encrypted Programming File |
| Game Maker Actions Library |
| Visual C++ Import Library |
| license | Visual Studio Binary License Data |
| licx | Visual Studio License Text |
| lid | Dylan Library |
| lif | HP-UX LIF File |
| lin | Valve Source Leak Pointfile |
| µVision Linker Control Data |
| link | CodeWarrior Link Data |
| Eclipse Link File |
| links | Links Programming Language Source Code |
| lino | LinoLab Source Code |
| linq | LINQPad Source Code |
| lipg | LiPG Parser |
| lis | HP OpenVMS List Data |
| lisp | Lisp Source Code |
| lit | Literate Haskell Script |
