| Extension | Description | File Type |
|---|
| jad | Java Application Descriptor File | Misc Files |
| jar | Java Archive File | Executable Files |
| java | Java Source Code File | Developer Files |
| jc | FlashGet Partial Download | Misc Files |
| jccfg3 | FlahGet Temporary File | Misc Files |
| jgw | JPG World file | Data Files |
| jhtml | Java HTML Web Page File | Web Files |
| jnlp | Java Web Start File | Web Files |
| jnt | Windows Journal Note File | Misc Files |
| job | Windows Task Scheduler Job File | System Files |
| joboptions | Adobe Acrobat Joboptions File | Text Files |
| joined | HJSplit Data File | Data Files |
| jp2 | JPEG 2000 File | Graphic Files |
| jpeg | JPEG Image File | Graphic Files |
| jpf | JPEG 2000 File | Graphic Files |
| jpg | JPEG | Graphic Files |
| jps | stereoscopic JPG File | 3D Files |
| jpx | JBuilder Project File | Developer Files |
| js | JScript Executable File | Executable Files |
| jsf | Fireworks Batch Script File | Settings Files |
| json | JavaScript Object Notation File | Developer Files |
| jsp | Java Server Page | Web Files |
| jtd | Ichitaro Document File | Document Files |
| jwc | NTI JewelCase Maker File | Misc Files |
| jxr | JPEG XR Files | Graphic Files |