| Abbreviation | Definition |
|---|---|
| JS | JavaScript language source code file (script) |
| JSM | Jigsaw file (JugWin) |
| JSS | JugWin Jigsaw file |
| JTF | Bitmap graphics (JPEG Tagged Interchange Format) |
| JTF | Fax (Hayes JT Fax) |
| JUT | Jutvision Scene (Jutvision) |
| JW | JustWrite Text document |
| JWL | JustWrite Library |
| JZZ | Spreadsheet (Jazz) |
| K3D | Description of macro language (3DS) |
| KAR | Karaoke (MIDI music with word track) |
| KAR | Precompiled .prg for KARAT file |
| KB | Keyboard script file |
| KB | Program source (Knowledge Pro) |
| KBD | Keyboard mapping (LocoScript - Signature - Procomm Plus) |
| KBM | KeyBoard Mapping file |
| KCL | Kyoto Common Lisp language source code file |
| KDC | Kodak Digital Camera PhotoEnhancer file Bitmap graphics |
| KDK | (Kodak proprietary decimated TIFF format - Bitmap graphics |
| KEX | KEDIT Macro |