Yes — anthopic.online has IPv6.

Has both IPv4 (A) and IPv6 (AAAA) addresses.

B
IPv6 readiness
Works over IPv6, with one gap: its mail servers lack IPv6.
Website over IPv6
anthopic.online has 2 IPv6 addresses and answers on every one we tested.
✓ 2606:4700:3031::6815:2521 answers · 443✓ 2606:4700:3031::ac43:cb6f answers · 443
yes
Mail servers (MX) have IPv6
None of the mail servers has an AAAA record.
mail.anthopic.online ✗
no
Nameservers have IPv6
2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.
rosa.ns.cloudflare.com ✓uriah.ns.cloudflare.com ✓
yes
HTTPS over IPv6 · not part of the grade yet
Answered over IPv6 with a server error (HTTP 525) — can't tell whether that's specific to IPv6.
https://anthopic.online/ via 2606:4700:3031::6815:2521 → 525
?
 Which outside scripts, fonts, payments or chat anthopic.online loads from have no IPv6.
 Load anthopic.online over IPv6 from up to six other places — a second opinion.

What's keeping anthopic.online from an A

  1. Mail servers without IPv6
    mail.anthopic.online has no AAAA record, so mail from IPv6-only servers can't reach it directly. If a provider runs your mail, that's their setting; if you run it, add AAAA records for these hosts.

Check again

anthopic.online  Has IPv6

A (IPv4)104.21.37.33
172.67.203.111
AAAA (IPv6)2606:4700:3031::6815:2521
2606:4700:3031::ac43:cb6f

Browsers on dual-stack networks will usually pick IPv6 here (the "Happy Eyeballs" algorithm races both and prefers v6).

Copy the evidence — a citation-ready record of this measurement

 Permanent link: aaaa.bot/r/UzhPI4E6T2 · How we measure

Checked 2026-11-13 01:54:08 UTC. Full DNS report: dns.pizza/domain/anthopic.online · Age, certificate and blocklists: how.is/anthopic.online · JSON: /api/v1/anthopic.online