| 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 |
| jcw | JCreator Workspace |
| jcw | JCross Data |
| jd | Doclava Javadoc Template |
| jd | JDownloader Data |
| jd | Jigsaw Terminal Data |
| jda | Winphone Fax Send Journal Data |
| jdb | Winphone Fax Receive Journal Data |
| jdbg | Embedded JCL Debug Info |
| jdc | JDownloader Container |
| jdd | Globus Toolkit Job Description Document |
| jdf | Job Definition Format File |
| jdl | gLite Job Description Language File |
| jds | JDataStore Database |
| jdsu | ACTIX Analyzer JDSU Data |
| jdt | Accelio Capture Classic Filler Data |
| jdt | Oracle Documaker GenData Rules Data |
| jdx | JCAMP-DX Format Data |
| jdx | JSpell Dictionary Data |
| je | SAP Fiori Journal Entry Data |
| jeb | PENSIM Output |
| jed | Xilinx JEDEC Data |
| jedec | Xilinx JEDEC Data |
| jef | Janome Embroidery Data |
| jeff | Java Explanation Facility Framework Data |
| jem | Optifine JSON Entity Model |
| jet | California JET Data |
| jetinc | Eclipse IDE Template Fragment Data |
| jfd | FormWare Job Definition |
