Yes — yale.edu has IPv6.

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

Measured 2026-11-02 16:56 UTC. We reuse a result for up to a week, so we aren't testing the same site over and over. Check yale.edu now

IPv6 readiness

Website, mail and DNS all work over IPv6.

Website over IPv6 yale.edu has 4 IPv6 addresses and answers on every one we tested. ✓ 2a04:4e42:400::645 answers · 443✓ 2a04:4e42:200::645 answers · 443✓ 2a04:4e42::645 answers · 443✓ 2a04:4e42:600::645 answers · 443	yes
www over IPv6 www.yale.edu has 4 IPv6 addresses and answers on every one we tested. ✓ 2a04:4e42::645 answers · 443✓ 2a04:4e42:200::645 answers · 443✓ 2a04:4e42:400::645 answers · 443✓ 2a04:4e42:600::645 answers · 443	yes
Mail servers (MX) have IPv6 Every mail server has an AAAA record. yale-edu.mail.protection.outlook.com ✓	yes
Nameservers have IPv6 3 of 5 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up. pks1302-103.net.yale.edu ✗pks1302-102.net.yale.edu ✗ns1.bluecatdns.org ✓ns1.bluecatdns.net ✓ns1.bluecatdns.com ✓	yes

First measured 2026-11-02; last confirmed 2026-11-02.

HTTPS over IPv6 · not part of the grade yet
Loads over IPv6 with a valid certificate after 1 redirect: HTTP 200.

https://yale.edu/ via 2a04:4e42:400::645 → 301https://www.yale.edu/ via 2a04:4e42::645 → 200

works

Nothing keeping you from an A

Nothing to fix
Show it off: add the badge to your README.
[![IPv6](https://aaaa.bot/badge/yale.edu.svg)](https://aaaa.bot/yale.edu)

Check again

yale.edu Has IPv6

A (IPv4)	151.101.66.133 23.185.0.4 23.185.0.2 151.101.2.133 151.101.130.133
AAAA (IPv6)	2a04:4e42:400::645 2a04:4e42:200::645 2a04:4e42::645 2a04:4e42:600::645

www.yale.edu Has IPv6

Alias of	pantheon-systems.map.fastly.net
A (IPv4)	151.101.2.133 151.101.66.133 151.101.130.133 151.101.194.133
AAAA (IPv6)	2a04:4e42::645 2a04:4e42:200::645 2a04:4e42:400::645 2a04:4e42:600::645

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: yale.edu
Measured 2026-11-02 16:56:30 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    151.101.66.133, 23.185.0.4, 23.185.0.2, 151.101.2.133, 151.101.130.133
AAAA (IPv6): 2a04:4e42:400::645, 2a04:4e42:200::645, 2a04:4e42::645, 2a04:4e42:600::645
www AAAA:    2a04:4e42::645, 2a04:4e42:200::645, 2a04:4e42:400::645, 2a04:4e42:600::645

Readiness grade A: Website, mail and DNS all work over IPv6.
- Website over IPv6: yale.edu has 4 IPv6 addresses and answers on every one we tested.
    2a04:4e42:400::645: answers (TCP 443)
    2a04:4e42:200::645: answers (TCP 443)
    2a04:4e42::645: answers (TCP 443)
    2a04:4e42:600::645: answers (TCP 443)
- www over IPv6: www.yale.edu has 4 IPv6 addresses and answers on every one we tested.
    2a04:4e42::645: answers (TCP 443)
    2a04:4e42:200::645: answers (TCP 443)
    2a04:4e42:400::645: answers (TCP 443)
    2a04:4e42:600::645: answers (TCP 443)
- Mail servers (MX) have IPv6: Every mail server has an AAAA record.
- Nameservers have IPv6: 3 of 5 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): Loads over IPv6 with a valid certificate after 1 redirect: HTTP 200.
    https://yale.edu/ via 2a04:4e42:400::645 -> HTTP 301, certificate: valid
    https://www.yale.edu/ via 2a04:4e42::645 -> HTTP 200, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/lATFvH8owT

Permanent link: aaaa.bot/r/lATFvH8owT · How we measure

Checked 2026-11-02 16:56:30 UTC. Full DNS report: dns.pizza/domain/yale.edu · Age, certificate and blocklists: how.is/yale.edu · JSON: /api/v1/yale.edu