UltraDefrag is a disk defragmentation utility for Microsoft Windows.

Prior to version 8.0.0 it was released under the GNU General Public License.

The only other Windows-based defragmentation utility licensed under the GNU GPL was JkDefrag, discontinued in 2008.

Their enhanced version, released under a proprietary license, features automatic defragmentation, disk cleanup before defragmentation, graphical interface for setting user preferences, optimization of solid state drives, full compatibility with Windows 11 and 10, and is said to have much faster disk processing algorithms.

[3] Jean-Pierre André, one of the developers of NTFS-3G, has created a fork of UltraDefrag 5 that runs on Linux.