Yes — sso.oreilly.com has IPv6.

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

A
IPv6 readiness
Website, mail and DNS all work over IPv6.
Website over IPv6
sso.oreilly.com has 2 IPv6 addresses and answers on every one we tested.
✓ 2606:4700:440b::ac40:99f9 answers · 443✓ 2a06:98c1:3101::6812:2207 answers · 443
yes
Mail servers (MX) have IPv6
No MX records, so mail goes to the domain's own address (implicit MX). It has an AAAA record.		yes
Nameservers have IPv6
6 of 6 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.
a13-64.akam.net ✓a3-67.akam.net ✓a20-66.akam.net ✓a16-65.akam.net ✓a1-225.akam.net ✓a4-64.akam.net ✓
yes
HTTPS over IPv6 · not part of the grade yet
Redirects to oreilly.com, which has no IPv6 address — so IPv6 visitors end up needing IPv4 after all.
https://sso.oreilly.com/ via 2606:4700:440b::ac40:99f9 → 302https://oreilly.com/ · redirects to oreilly.com, which has no IPv6 address
problem
 Load sso.oreilly.com over IPv6 from up to six other places — a second opinion.

Nothing keeping you from an A

  1. A redirect leads off IPv6
    Redirects to oreilly.com, which has no IPv6 address — so IPv6 visitors end up needing IPv4 after all. Give the redirect target IPv6 too, or redirect somewhere that has it.

Check again

sso.oreilly.com  Has IPv6

Alias oflearning-cd-vdue44vdsl9llt0m.edge.tenants.oreilly.auth0app.com → learning.oreilly.auth0app.com → plwpo8.oreilly.auth0app.com.pivot.prod.auth0edge.com → ingress.oreilly.auth0app.com.cdn.cloudflare.net
A (IPv4)104.18.34.7
172.64.153.249
AAAA (IPv6)2606:4700:440b::ac40:99f9
2a06:98c1:3101::6812:2207

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/0ubQe-AyN9 · How we measure

Checked 2026-11-01 16:40:39 UTC. Full DNS report: dns.pizza/domain/sso.oreilly.com · JSON: /api/v1/sso.oreilly.com