I know the speeds would obviously be a key factor, but is there any spot on way to tell if a device is USB 2.0 or 3.0 such as a USB flash drive?
USB3 has more pins than USB2.
USB1 and USB2 have four pins, two for power, one pair for data. USB3 has those four in the standard place, and two extra pairs for 'superspeed' communication.
Wikipedia has two pictures of this, though I must admit is is not clear when you look at them. It should be much easier when looking at a physical device. (Note that both USB3 ports are blue in the pictures below, which matches @mdpc answer.)
Added the picture from Scott's link here:
On macOS, System Information indicates the USB speed, per this answer on askdifferent
For reference, USB speeds/specs are as follows:
USB 1.x - 12Mb/sec USB 2.0 - 480Mb/sec USB 3.0 - 5Gb/s USB 3.1 - 10Gb/s
lsusb per this answer on askubuntu:
...and I haven't confirmed it, but apparently this is the
lsusb equivalent with Powershell:
I find looking at the color of the port is an ok rule of thumb, but I have had it be wrong more then once, so it doesn't really give you the answer. I have usb sticks with blue connectors that are usb 2, and I have pc ports that are USB 3.0 that are black, so its kind of a crap shoot
I have noticed, most usb 3.0 devices that I have, actually say USB 3.0 right on the male port, etched into the metal.
If you want to know definitively, you can use the USB Device Tree Viewer (http://www.uwe-sieber.de/usbtreeview_e.html#download) to view in depth information about the device, including the USB specification.
I realize this is a kind of old post, but it was still on the first page of google search results when trying to find how to identify usb 2 vs 3. Hopefully this info is helpful to someone else.