| .J | Oracle Corporation | Rasterbilledfiler | Java Source File | Vim | Bram Moolenaar |
| .J2K | Joint Photographic Experts Group | Rasterbilledfiler | JPEG 2000 Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JAS | Open Source | Rasterbilledfiler | Cheetah3D Model File | Unity Technologies Unity | Unity Technologies |
| .JB2 | Joint Bi-level Image Group | Rasterbilledfiler | JBIG2 Image | OmniPage | Nuance |
| .JBF | Corel | Rasterbilledfiler | Paint Shop Pro Browser Cache File | PaintShop Pro | Corel |
| .JBG | Joint Bi-level Image Group | Rasterbilledfiler | Joint Bi-level Image Group File | Graphics Converter Pro | Newera Software Technology, Inc. |
| .JBIG | Joint Bi-level Image Group | Rasterbilledfiler | Joint Bi-level Image Group File | Graphics Converter Pro | Newera Software Technology, Inc. |
| .JBIG2 | Joint Bi-level Image Group | Rasterbilledfiler | JBIG2 Bitmap Image | Graphics Converter Pro | Newera Software Technology, Inc. |
| .JBR | Corel | Rasterbilledfiler | Paint Shop Pro Brushes File | ACD Systems ACDSee | ACD Systems |
| .JFI | Joint Photographic Experts Group | Rasterbilledfiler | JPEG File Interchange Image | Adobe Photoshop | Adobe Systems Incorporated |
| .JFIF | Unknown Developer | Rasterbilledfiler | JPEG File Interchange Format | Internet Explorer | Microsoft Corporation |
| .JFX | j2 Global, Inc. | Rasterbilledfiler | J2 jConnect Fax File | j2 Global Communications eFax | j2 Global, Inc. |
| .JIF | Joint Photographic Experts Group | Rasterbilledfiler | JPEG Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JLS | Freedom Scientific | Rasterbilledfiler | JAWS Data File | JAWS | Freedom Scientific |
| .JMG | Unknown Developer | Rasterbilledfiler | 16 Bit Adaptive RLE Compressed Bitmap Image | Unknown Software | Unknown Developer |
| .JMH | Unknown Developer | Rasterbilledfiler | JPEG File Interchange Format | Internet Explorer | Microsoft Corporation |
| .JP2 | Joint Photographic Experts Group | Rasterbilledfiler | JPEG 2000 Core Image File | MacPhun ColorStrokes | Macphun |
| .JPC | Joint Photographic Experts Group | Rasterbilledfiler | JPEG 2000 Code Stream File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JPE | Pierre-Emmanuel Gougelet | Rasterbilledfiler | JPEG Bitmap Image Format | XnView MP | XnSoft |
| .JPEG | Joint Photographic Experts Group | Rasterbilledfiler | JPEG Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JPF | Joint Photographic Experts Group | Rasterbilledfiler | JPEG 2000 Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JPG | Joint Photographic Experts Group | Rasterbilledfiler | JPEG Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JPG-LARGE | Zoner Software | Rasterbilledfiler | Large JPEG Image | Adobe Photoshop | Adobe Systems Incorporated |
| .JPG2 | Joint Photographic Experts Group | Rasterbilledfiler | JPEG 2000 Image | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JPG_ | Google | Rasterbilledfiler | Google Android General Picture Image | Google Android | Google |
| .JPG_128X96 | Google | Rasterbilledfiler | Android Picture | Google Android | Google |
| .JPG_160X120 | Google | Rasterbilledfiler | Android Picture | Google Android | Google |
| .JPG_160X128 | Google | Rasterbilledfiler | Android Picture | Google Android | Google |
| .JPG_320X240 | Google | Rasterbilledfiler | Android Picture | Google Android | Google |
| .JPS | Open Source | Rasterbilledfiler | Akeeba Backup Archive | Akeeba eXtract Wizard | Open Source |
| .JPX | Embarcadero Technologies | Rasterbilledfiler | JBuilder Project | JBuilder | Embarcadero Technologies |
| .JTF | Various Developers | Rasterbilledfiler | JPEG Tagged Interchange Format | Adobe Illustrator CC | Adobe Systems Incorporated |
| .JWL | Roxio | Rasterbilledfiler | Roxio Jewel Case File | Roxio Creator NXT Pro 5 | Roxio |
| .JXR | Microsoft Corporation | Rasterbilledfiler | JPEG XR Image | Adobe Photoshop | Adobe Systems Incorporated |
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