HTTP/3 is the latest version of the HTTP designed and used primarily for transferring data over the web. It is designed to be more efficient, faster, and more reliable, especially in conditions where network connections might be less stable or slower.
HTTP/3 is built upon the transport protocol QUIC (Quick UDP Internet Connections), which was initially designed and developed at Google. Unlike its predecessors, HTTP/3 uses UDP instead of TCP for data transmission. QUIC also includes TLS v1.3 security protocol, and then data encryption is shifted down from the application layer to the transport layer. Thanks to this, fewer round-trips are required to establish a connection because only one handshake is required. Consequently, HTTP/3 always requires an encrypted connection.
Another significant improvement is solving the head-of-line blocking problem thanks to stream multiplexing by QUIC. Therefore, a single undelivered packet doesn't block all streams.
We've performed thorough HTTP/3 performance tests. They proved significant performance gain, especially in poor cellular network conditions. Therefore, it may have a noticeable positive impact on increasing conversion rates for online businesses.
HTTP/3 support is enabled by default in most major browsers and operating systems. However, a challenge might be enabling it server-side because not all web servers or load balancers currently support it. Some open-source tools may require compiling ones from sources.
Nevertheless, HTTP/3 is a significant step forward since when HTTP/2 replaced HTTP/1.1.