JkDefrag is a free disk defragment and optimize utility for Windows released under the GNU General Public License. JkDefrag is based on the standard defragmentation API by Microsoft, a system library that is included in Windows 2000, 2003, XP, and Vista. JkDefrag is therefore very solid and there is no risk of losing data.

There are 3 types of program:

1. JkDefrag.exe (Windows version) - No installation or configuration needed.
2. JkDefragCmd.exe (Command line version)- It is designed to be run automatically in the background, or from administrator scripts.
3. JkDefragScreenSaver.scr + JkDefragScreenSaver.exe (Screen saver version) - It will appear in the list of screensavers as “JkDefrag screensaver” and can be used just like any other screensaver.

Different between JkDefrag and other defraggers:

• JkDefrag is free and open-source.
• Totally automatic, extremely easy to use.
• Optimized for daily use.
• Directories are moved to the beginning of the disk.
• Reclaims MFT reserved space after disk-full.
• Maintains a free space for temporary files.
• Can defrag individual directories and files.
• Can be used from the commandline.
• Can be used as a screen saver.
• Sources available, can be customized.



JkDefrag shows a high-detail map of the harddisk, refreshed 3 times per second. Bottom-left of the window is the beginning of the harddisk. The colors used are:

• Black: empty
• Dark-green: in use
• Green: defragmented
• Yellow: fragmented
• Red: unmovable
• Pink: system files
• White: busy

When the JkDefrag is running you will see lot’s of messages zipping by showing you exactly what is happening. The messages are also stored in the logfile (”JkDefrag.log” or “JkDefragCmd.log”) for later inspection.

JkDefrag is compatible with Windows 2000/2003/XP/Vista/X64. You can download it from:

• Download JkDefrag v3.8 (320kb) for Windows 2000/2003/XP/Vista
• Download JkDefrag64 v3.8 (323kb) for Windows X64
• Download JkDefrag v3.8 sources (238kb) for Microsoft Visual C++ 2005