What is HTTP/3?
HTTP/3 is the latest version of the HTTP protocol, built on QUIC (a UDP-based transport protocol) instead of TCP, providing faster connection establishment, improved performance on unreliable networks, and elimination of head-of-line blocking.
How Does HTTP/3 Work?
While HTTP/2 solved many performance issues, it still relied on TCP, which suffers from head-of-line blocking at the transport layer: if a single TCP packet is lost, all streams on that connection are stalled until the lost packet is retransmitted. HTTP/3 replaces TCP with QUIC, a transport protocol that runs over UDP and implements its own reliable delivery independently for each stream. This means a packet loss on one stream does not affect others.
QUIC also integrates TLS 1.3 encryption directly into the transport layer, reducing the number of round trips needed to establish a secure connection from two or three down to just one (or even zero for repeat connections). This makes HTTP/3 particularly beneficial for mobile users and connections with high latency or packet loss. Major CDNs and browsers already support HTTP/3, and it is gradually becoming the default for web traffic.