Defragmentation can improve data access performance for some drives, but is less useful for others; your operating system is also a factor. In short, there is no easy answer.

The term defragment refers to the process of reorganising separate fragments of related data, for example a file, in order to improve access time. If your computer or laptop stores data on a mechanical hard disk drive (HDD), then defragging can be advantageous. HDDs store data in sectors, and one file could be broken up across multiple sectors. To read a file, your HDD’s read/write heads would then have to move around more, slowing down read speeds. Your operating system will do its best to store sectors consecutively, but if there is not enough consecutive space, the file will be split, or fragmented. If your computer or laptop is running slow, and it stores data on an HDD, defragmenting might speed things up.

On the other hand, if your machine stores data on a solid-state drive, then defragmentation will not be of benefit. On the contrary, it will decrease the drive’s lifespan. SSD’s store data on NAND flash chips, and contain no moving parts. Because there are no read/write heads that are having to move about looking for sectors, seek time is negligible. SSDs also have a limited number of cycles they can withstand, so defragging an SSD will actually do more harm than good.

In terms of operating system, if you’re using an HDD on a Windows machine, it will probably already be set up automatically, but you can change the frequency as you please, or run on-demand defrags of your HDD. If you’re using a Mac, even with an HDD, then defragmentation is not necessary. This is because the file system Apple uses (HFS+ and more recently APFS) prevents files from becoming defragmented, and if they do, automatically defrags.