Defraggler is a free disk defragmentation tool that allows users to defragment individual files, folders, or the entire hard drive quickly and efficiently. The software offers advanced options such as scheduled defragmentation, automatic shutdown after defragmentation, and the ability to exclude specific files or folders from the process. Defraggler also provides a clear visualization of the fragmentation status of files and drives, making it easy for users to prioritize defragmentation based on their needs.