ALPN (Application-Layer Protocol Negotiation)

ALPN (Application-Layer Protocol Negotiation) is a protocol that allows a client and server to efficiently agree on which application protocol to use—like HTTP/1.1 or HTTP/2—during the initial connection handshake. Instead of separately negotiating after connecting, ALPN enables this decision to happen seamlessly within the secure TLS handshake, saving time and improving performance. It ensures both parties are synchronized on the protocol they will use, facilitating faster, more secure, and more efficient communication between web browsers and servers.