Happy Eyeballs
SVCB/HTTPS Record Usage Test

SVCB and HTTPS DNS records (RFC 9460) can carry ipv6hint parameters with addresses a client may connect to. For https:// origins, clients are expected to use the HTTPS record — the generic SVCB record (type 64) is reserved for other protocols and should never be used.

In this test, the AAAA record, the HTTPS record's ipv6hint, and the SVCB record's ipv6hint each point to a different IPv6 address of our server. The address your browser connects to therefore reveals which record it used. We test four scenarios: all record types published together, only the HTTPS record, only the SVCB record (a connection here would violate RFC 9460), and only an AAAA record as control. This test is IPv6-only and requires IPv6 connectivity.