| jhd | WCAD01 Job Information Data |
| jhm | JavaHelp Map |
| jia | Digital Photo Navigator Album |
| jib | Sam2p JIB File |
| jjf | FlashJester Jugglor Data |
| jjjs | Claris Organizer Data |
| jks | Java Key Store |
| jlb | JDiveLog Logbook File |
| jlk | JET 3270 License Key Data |
| jlm | ILOG JViews License Manager Keys Data |
| jlp | Jumplist Extender Data |
| jlr | JetAudio Lyric Data |
| jlt | HP SmartStream Print |
| jm3 | BlastMetriX 3D Data |
| jmb | Juniper Message Bundle Data |
| jmf | Job Messaging Format File |
| jmp | JMP Data |
| jmt | JMatch Data |
| jmx | JMix Data |
| jn1 | BibExcel Journal Data |
| jnl | Ingres Journal Data |
| jnl | WinDev Log |
| jns | JANIS XML Data |
| job | MicroSim PCBoard External Job Data |
| job | USoft Job Definitions Data |
| job | VecTor5 Job Data |
| job | Windows Task Scheduler Job Object |
| jobs | VirtualDub Jobs Data |
| jod | Microsoft Jet OLEDB |
| joda | Joost Open Distribution Archive |
| jof | SmartCAM Job Operations File |
| joh | Zero 88 Jester ML Update Help Data |
| joined | HJSplit Data |
| joml | JOOB Object Modelling Language Data |
| jor | Microsoft SQL Server Journal Data |
