exFAT is a file system designed for flash based storage such as USB flash drives, SD cards and external SSDs. It was created to overcome the 4 GB single file size limit of the older FAT32, while staying lighter and simpler than a full featured system like NTFS.
One of exFAT's main strengths is broad cross platform compatibility. It can be read and written natively by current versions of Windows and macOS, and by many other devices such as cameras, game consoles and media players, which makes it a practical default for drives that need to move between different operating systems.
For a general purpose external drive or flash drive that will be plugged into more than one type of computer, exFAT is usually the most convenient choice, unless a specific device requires FAT32 for compatibility reasons. See our guide to USB flash drives for more on choosing a file system.
