HTTP/3

HTTP/3, standardized as RFC 9114, is the third major version of the Hypertext Transfer Protocol. It carries the same HTTP semantics as earlier versions but maps them onto QUIC, a transport built on UDP rather than TCP. That single change addresses the connection-level head-of-line blocking that HTTP/2 could not fully escape while still riding on TCP.

• QUIC transport - Runs over UDP with streams that are independent, so a lost packet on one stream no longer stalls the others.
• Built-in TLS 1.3 - Encryption is part of the transport rather than a layer bolted on top, making secure-by-default the only mode.
• Faster connection setup - Combines transport and cryptographic handshakes to reduce round trips, with 0-RTT resumption for returning clients.
• Connection migration - A session survives a network change — such as moving from Wi-Fi to cellular — without re-establishing the connection.

For API providers, HTTP/3 mostly arrives through CDNs, edge networks, and modern gateways rather than through changes to application code, since the semantics API consumers depend on are unchanged. When I look at where the industry is heading, HTTP/3 is the transport that matters most for mobile and high-latency clients, and its connection migration is a quietly important property for long-lived agentic and streaming API sessions that must survive shifting network conditions.