You can choose the corresponding solutions according to different reasons. Next, this article will introduce 8 methods to solve the "WD external hard drive slow transfer rate" problem in turn.
How to Increase Transfer Speed of External Hard Drive
It's connected to a USB 3 bus, and it's a USB 3 drive. I get, at the most, 9MB/s read and write. “I've got a 5TB WD easystore, perfectly healthy, but the speeds are unbearably slow in my Windows 10. User Case: USB 3.0 External Hard Drive Extremely Slow Transfer