| jcamp | JCAMP-DX Format Data |
| jcd | FlashGet Download Database |
| jceks | Java Cryptography Extension KeyStore |
| jch | CelLab Population History Log |
| jcl | JCloze Data |
| jcn | JobClock.NET TimeSummit Data |
| jcp | CelLab Pattern Data |
| jcp | Microsoft Exchange ESE Checkpoint File |
| jcrypt | JCrypt Data |
| jcsk | JetCast Skin Data |
| jcv | Garmin City Navigator Junction View |
| jcvib | Joy-Con Vibration Data |
| jcw | JCreator Workspace |
| jcw | JCross Data |
| jcx | JetAudio JetChat Data |
| jd | Doclava Javadoc Template |
| jd | JDownloader Data |
| jd | Jigsaw Terminal Data |
| jda | Winphone Fax Send Journal Data |
| jdb | Siren Jukebox Database |
| jdb | Winphone Fax Receive Journal Data |
| jdbg | Embedded JCL Debug Info |
| jdc | JDownloader Container |
| jdd | Globus Toolkit Job Description Document |
| jde | Cariverona Data |
| jdf | JAWS Voice Synthesizer Data |
| jdf | Job Definition Format File |
| jdl | gLite Job Description Language File |
| jds | JDataStore Database |
| jdsu | ACTIX Analyzer JDSU Data |
