A disk defragmenter is a software tool designed to optimize the performance of a computer's hard drive. Over time, files on a hard drive can become fragmented, meaning they are stored in non-contiguous spaces. This fragmentation can slow down data access and overall system performance. A disk defragmenter reorganizes these files, placing them closer together to improve efficiency. Using a disk defragmenter can lead to faster file retrieval and smoother operation of the operating system. Most modern operating systems, like Windows and macOS, include built-in defragmentation tools. Regularly defragmenting a hard drive can help maintain optimal performance, especially for traditional HDDs.