| Extension | 描述 | 檔案格式 |
|---|
| jad | Java Application Descriptor File | Misc Files |
| jar | Java Archive File | 執行檔 |
| java | Java Source Code File | Developer Files |
| jc | FlashGet Partial Download | Misc Files |
| jccfg3 | FlahGet Temporary File | Misc Files |
| jgw | JPG World file | 資料檔 |
| jhtml | Java HTML Web Page File | 網頁檔案 |
| jnlp | Java Web Start File | 網頁檔案 |
| jnt | Windows Journal Note File | Misc Files |
| job | Windows Task Scheduler Job File | 系統檔案 |
| joboptions | Adobe Acrobat Joboptions File | 文字檔 |
| joined | HJSplit Data File | 資料檔 |
| jp2 | JPEG 2000 File | 圖檔 |
| jpeg | JPEG Image File | 圖檔 |
| jpf | JPEG 2000 File | 圖檔 |
| jpg | JPEG | 圖檔 |
| jps | stereoscopic JPG File | 3D Files |
| jpx | JBuilder Project File | Developer Files |
| js | JScript Executable File | 執行檔 |
| jsf | Fireworks Batch Script File | 設定檔 |
| json | JavaScript Object Notation File | Developer Files |
| jsp | Java Server Page | 網頁檔案 |
| jtd | Ichitaro Document File | 文件檔案 |
| jwc | NTI JewelCase Maker File | Misc Files |
| jxr | JPEG XR Files | 圖檔 |