| jui | QT Jambi User Interface Data |
| jwg | OpenScript Script |
| jwp | CloudTran Build Properties |
| jwr | Rocket LegaSuite GUI Runtime |
| jws | Java Web Service |
| jx | Cocoon JX Template |
| jy | Jython Script |
| k7p | STEP 7 Lite Project |
| kb | Borland C++ Keyboard Script |
| kc | KeyKit Collection |
| kci | Visual Studio .NET DB Project Indexing Options |
| kct | Keyman Developer Customisation Source File |
| kd | Koara Source Code |
| kdevdlg | KDevelop Dialog Box |
| kdevelop | KDevelop Project |
| kdevprj | KDevelop Project |
| kdmp | Windows CE Crash Dump File |
| kev | QNX System Profiler Event Log |
| kfb | Pyke Knowledge Fact Base |
| kgi | Kokogut Module Interface File |
| kjp | KJP Source Code |
| kkm | Kkrunchy Map Data |
| kl | Haxial Compiler KL Source |
| kl3 | KL3 Source Code |
| km3 | Kernel MetaMetaModel File |
| kmk | VirtualBox kBuild Makefile |
| kmn | Keyman Developer Keyboard Source File |
| ko | Linux 2.6 Kernel Object |
| kodu | Kodu Game |
| kof | Kylix Options File |
| koi | Kokogut Module Interface File |
| kop | Kokogut Compiler Options File |
| kpp | Keyman Developer Product Installer Source File |
| kps | Keyman Developer Package Source File |
| kpz | Komodo IDE Compressed Package |
