HTTP3 rides UDP while HTTP2 stays safe over TCP
HTTP/3 runs over QUIC and UDP, commonly on port 443. HTTP/2 streams on a TCP connection share an ordered byte stream, so a missing segment can stall delivery for unrelated requests. QUIC provides ordered delivery per stream: losing data on one stream need not block delivery on another. Connection-wide congestion control and HTTP dependencies can still affect several streams; this is not independent congestion control for every stream. ...