UASP stands for USB Attached SCSI Protocol. It is a way for external storage devices, such as external SSDs and some hard drive enclosures, to communicate with a computer more efficiently than the older Bulk-Only Transport method that earlier USB storage relied on.
The main advantage of UASP is command queuing, which allows multiple read and write requests to be processed in a more overlapping, efficient way, reducing overhead and improving real world speed, particularly with fast external SSDs that would otherwise be held back by an older transfer protocol.
UASP support depends on the drive enclosure, the cable and the computer's own driver support all lining up, and a device can silently fall back to the older method if any part of the chain does not support it. Checking a product's specification for explicit UASP support is worthwhile when buying external storage meant to run at full speed. See our external SSD guide for more.
