Having this second space allows the manufacturer to use a single printed circuit board for more than one storage size device. USB connector cover or cap — reduces the risk of damage, prevents the entry of dirt or other contaminants, and improves overall device appearance. Some flash drives use retractable USB connectors instead. Others have a swivel arrangement so that the connector can be protected without removing anything.
Transport aid — the cap or the body often contains a hole suitable for connection to a key chain or lanyard. Connecting the cap, rather than the body, can allow the drive itself to be lost. Some drives offer expandable storage via an internal memory card slot, much like a memory card reader. A USB Drive in the shape of a key While some manufacturers are competing for the smallest size  with the biggest memory,  some manufacturers differentiate their products by using elaborate housings, which are often bulky and make the drive difficult to connect to the USB port.
Because the USB port connectors on a computer housing are often closely spaced, plugging a flash drive into a USB port may block an adjacent port. Such devices may carry the USB logo only if sold with a separate extension cable. Such cables are USB-compatible but do not conform to the USB standard. USB flash drives with images of dragons, cats or aliens are very popular in Asia.
Flash file system Most flash drives ship preformatted with the FAT32 , or exFAT file systems. The ubiquity of the FAT32 file system allows the drive to be accessed on virtually any host device with USB support. Also, standard FAT maintenance utilities e. However, because a flash drive appears as a USB-connected hard drive to the host system, the drive can be reformatted to any file system supported by the host operating system. Defragmenting Flash drives can be defragmented.
There is a widespread opinion that defragmenting brings little advantage as there is no mechanical head that moves from fragment to fragment , and that defragmenting shortens the life of the drive by making many unnecessary writes. Even distribution Some file systems are designed to distribute usage over an entire memory device without concentrating usage on any part e. Some USB flash drives have this ' wear leveling ' feature built into the software controller to prolong device life, while others do not, so it is not necessarily helpful to install one of these file systems.
Therefore, USB flash units can be partitioned just like hard disk drives. Longevity[ edit ] The memory in flash drives is commonly engineered with multi-level cell MLC based memory that is good for around 3,, program-erase cycles,  but some flash drives have single-level cell SLC based memory that is good for around , writes. There is virtually no limit to the number of reads from such flash memory, so a well-worn USB drive may be write-protected to help ensure the life of individual cells.
Good flash drives have fast sequential read speeds for accessing data on the drive and sequential write speeds for copying data to the drive. Of the two, write speeds are almost always lower and can vary wildly based on the type of memory and controller a drive uses. Flash drives should maintain consistent performance during large file transfers. Plus, most flash drives are pretty durable, and software encryption can easily protect all the data on your drive.
Few people have only USB-C devices, and most devices still lack USB-C entirely. We instead looked at dual-port drives, which have both USB-A and USB-C connectors. These designs maximize compatibility while ensuring you can plug the drive into future devices. We also tested our USB-A picks with a cheap USB-C adapter. Our picks, plus our favorite USB-A—to—USB-C adapter dongle. How we tested We used CrystalDiskMark to benchmark each drive on Windows and Blackmagic Disk Speed Test on a Mac.
We also tested real-world read and write speeds by copying 14 GB of media files from one drive to another. We performed each test three times and averaged the results. Although we chose drives based on computer use, we tested them for compatibility on a MacBook Air, a Dell XPS 13, an LG television, and a Sony PlayStation 4.