Yes — sso.oreilly.com has IPv6.

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

This is a saved measurement from 2026-11-01 16:40 UTC. Check sso.oreilly.com live now

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

Nothing keeping you from an A

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 of	learning-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

IPv6 measurement: sso.oreilly.com
Measured 2026-11-01 16:40:39 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    104.18.34.7, 172.64.153.249
AAAA (IPv6): 2606:4700:440b::ac40:99f9, 2a06:98c1:3101::6812:2207

Readiness grade A: 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 (TCP 443)
    2a06:98c1:3101::6812:2207: answers (TCP 443)
- Mail servers (MX) have IPv6: No MX records, so mail goes to the domain's own address (implicit MX). It has an AAAA record.
- Nameservers have IPv6: 6 of 6 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up.

Reachability = a TCP connection opened on port 443 (or 80).

HTTPS over IPv6 (not graded): 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 -> HTTP 302, certificate: valid
    https://oreilly.com/ (redirects to oreilly.com, which has no IPv6 address)
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/0ubQe-AyN9

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