Disk Defragmenter is a utility in Microsoft Windows designed to increase access speed by rearranging files stored on a disk to occupy contiguous storage locations, a technique called defragmentation.
Defragmenting your hard disk actually shouldn’t be necessary on modern versions of Windows.It’ll automatically defragment mechanical hard drives in the background. Solid-state drives don’t really need traditional defragmentation, although modern versions of Windows will “optimize” them — and that’s fine.
You shouldn’t worry about defragmentation most of the time.However, if you do have a mechanical hard drive and you’ve just put a lot of files on the drive — for example, copying a huge database or gigabytes of PC game files — those files might be defragmented because Windows hasn’t gotten around to defragmenting them yet. In this situation, you might want to open the disk defragmenter tool and perform a scan to see if you need to run a manual defrag program.