TBW stands for terabytes written, and it is a rating manufacturers give to solid state drives and some higher end flash drives to describe how much total data can be written to the device over its lifetime before the underlying NAND flash memory is expected to wear out.
A higher TBW figure generally indicates a drive built for heavier, more sustained write activity, such as frequent backups or use as working storage for large files, while a lower TBW figure is usually fine for a drive mainly used to store files that rarely change once written.
TBW is a useful way to compare the expected durability of external SSDs marketed for similar capacities and prices, though for typical everyday use, most drives will comfortably outlast their practical usefulness before reaching their TBW limit. See our external SSD guide for more on choosing a durable drive.
