HTTP/3 is an updated version of the HTTP protocol that uses UDP instead of TCP, resulting in reduced latency and improved connection reliability. It is built on top of the QUIC transport protocol developed by Google, offering benefits such as faster handshakes, always-on encryption, and improved performance on mobile networks. To enable HTTP/3, you need compatible browsers like Chrome and server stacks like Nginx with a QUIC patch or Caddy. Testing HTTP/3 can be done using browser dev tools or command line tools like curl, and monitoring tools like KeyCDN can help validate the protocol status. Adopting HTTP/3 can lead to faster and more secure applications, especially on poor networks.