| jsd | JAWS Script Documentation File |
| jsfl | Flash JavaScript |
| jsh | Jsh Script |
| jsh | JAWS Script Header |
| jsl | JMP Scripting Language File |
| jsm | JavaScript Module |
| jsm | JAWS Script Message File |
| jsp | Java Servlet |
| jspa | Java Servlet Alias |
| jspf | Java Server Page Fragment |
| jspx | Java Servlet XML |
| jss | JavaScript Style Sheet |
| jss | JAWS Script Source |
| jst | Code Crusader Symbol Database |
| jsx | Adobe ExtendScript File |
| jsxbin | Adobe ExtendScript Binary File |
| jsxinc | Adobe ExtendScript Include File |
| jtb | JavaCC Grammar File |
| jtr | JavaTest Results Data |
| ju | JU Source Code |
| judo | JudoScript Source Code |
| jug | Jug Code |
| jui | QT Jambi User Interface Data |
| jv | ICE JVCC Source Code |
| 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 |