HTTP/3

HTTP/3 is the third major version of HTTP, running over QUIC — a transport built on UDP rather than TCP. It keeps HTTP/2’s multiplexing but gives each stream independent delivery, folds the TLS handshake into the connection setup, and can migrate a connection across network changes without a reconnect.

Worked example: on a flaky mobile network, an HTTP/3 connection that loses a packet on one stream keeps delivering the others, and it can survive switching from Wi-Fi to cellular mid-download because the connection is identified by an ID, not an IP-and-port pair. Gotcha: it solves TCP’s head-of-line blocking by abandoning TCP entirely, so some corporate firewalls and middleboxes that only expect TCP can block or throttle QUIC, which is why clients keep an HTTP/2 fallback.