SVCB/HTTPS record
SVCB and HTTPS are DNS record types, both defined in RFC 9460, that let a zone publish service-connection hints -- such as which ALPN protocols a server supports (h2, h3) or a non-default port -- in the same DNS answer as the service's address, rather than leaving a client to discover them during the connection itself. HTTPS is a fixed specialization of the general-purpose SVCB record for web traffic specifically; a browser that resolves an HTTPS record for a domain can open a QUIC/HTTP-3 connection directly, skipping the extra round trip of first connecting over TCP and negotiating ALPN during the TLS handshake. Because the record is new relative to the rest of DNS, a resolver or client that doesn't understand it simply ignores it and falls back to ordinary A/AAAA resolution, so publishing one is additive rather than something that can break older clients.
By AdminKit team, Netbase JSC · Updated