3 services carry this tag in their source record. Tags come from the provider, not from us — a tag is a claim about what the service does, not proof that it does it well.
Check the TLS certificate a domain serves on port 443: whether it chains to a trusted root, matches the name (RFC 9525) and when it expires, with issuer, chain, key and signature algorithm, TLS version and coded findings...
DNS HTTPS/SVCB record lookup: service binding records that advertise HTTP/3 and HTTP/2 (ALPN), ECH and IP hints for a domain. Shows whether a site supports HTTP/3 at the DNS level. $0.01 per lookup.
HTTP/3 and modern-transport support: checks the DNS HTTPS record (alpn, ech, ipv4hint), the Alt-Svc response header for h3, and reports whether HTTP/3 (QUIC), HTTP/2 and Encrypted Client Hello are advertised. Useful for...