UltraDefrag is a free open-source disk defragmentation tool for Windows that can defragment and optimize hard drives and solid-state drives. It offers a simple and intuitive user interface, allowing users to easily analyze and defragment their disks. The software supports various defragmentation modes, including fast optimization, full optimization, and disk optimization. Additionally, it can defragment individual files and folders, exclude specific files and folders from defragmentation, and automatically schedule defragmentation tasks.