A:Answer USB 2.0 has a transfer rate of 480 Mbps, while USB 3.0 is rated at 4.8 Gbps. These are the specifications (theoretical), so actual speeds will vary, but 3.0 should still be much faster. Also 2.0 is limited to to 500 mA, while 3.0 stops at 900 mA. To make things more confusing, USB 3.0 has two levels: there is USB 3.0, also called USB 310 Gen 1, and there is USB 3.1, also called USB 3.1 Gen 2, which is 2x faster. In practical terms, however, you will find that only the more expensive/larger capacity pen drives will feature USB 3.1 (Gen 2). USB 3.1 is fully backward compatible with USB 3.0 and 2.0, while USB 3.0 is compatible with 2.0. By this I mean that they will connect, and work, but speed will be limited to the lower speed of any connector,. Further, USB 3.0 (3.1 Gen 1) is usually recognizable because the connector inside will be blue colored and have the letters "SS" (SuperSpeed), while 2.0 is black or white. USB 3.1 I (3.1 Gen 2) is turquoise colored. I say "usually" because cables or dongles ALWAYS will have this difference, but PCs don't--I have a top of the line Dell XPS, and all USB connectors are black (probably an aesthetic choice). There is also USB C, which is faster still and delivers up to 5 mA, but the connector is completely different: it looks like an oval, and can be inserted in both directions, whereas the preceding USBs had only one direction to connect. And if you wait long enough, USB 4.0 will be out in the not too distant future, so you can be further confused.
