USB 4.0, formally referred to as USB4, was released by the USB Implementers Forum on August 29, 2019. USB4 defines the interface architecture and not the connector type, but the Forum mandates the use of the USB-C connector for USB-4 ports and cables.
USB4 is based on the Thunderbolt 3 protocol, which Intel made royalty-free in 2019. As a result, it offers a maximum bandwidth of 40Gbps, and gamers will be pleased to learn that USB4 is finally fast enough to support external GPUs. As with other USB versions, USB4 is backward-compatible with older generations, such as USB 3.2 and USB 2.0.
USB4 supports several alternate modes, including Thunderbolt, DisplayPort, and MHL over Alt Mode but drops the HDMI Alt Mode from USB 3.0. Rather than as an optional feature, USB4 certification for laptops and docks requires that all downstream USB-C ports support DisplayPort 2.0, which makes these ports capable of displaying 8K and 16K video at 60Hz.
It also supports DisplayPort and PCIe tunneling, although the latter is optional. This allows for faster transfer rates when sending mixed data. The mini-mum power delivery output also goes to 7.5W, up from 4.5W in USB 3.0, but the maximum power delivery remains 240W.
Another thing USB4 does better than its predecessors is that it has logos that are more informative. You are now better to tell how fast your USB4 Type-C cable can transfer data and the maximum power output it supports by checking the spec sheet or the ends.