Yes — castorpb.dev has IPv6.

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

IPv6 readiness

Website, mail and DNS all work over IPv6.

Website over IPv6 castorpb.dev has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3031::6815:4654 answers · 443✓ 2606:4700:3031::ac43:dde2 answers · 443	yes
www over IPv6 www.castorpb.dev has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3031::ac43:dde2 answers · 443✓ 2606:4700:3031::6815:4654 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 2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up. nicole.ns.cloudflare.com ✓rob.ns.cloudflare.com ✓	yes

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

https://castorpb.dev/ via 2606:4700:3031::6815:4654 → 302https://summer-silence-5c5a.cloudflareaccess.com/cdn-cgi/access/login/castorpb.dev?kid=273aa8d7c518f67bf9a859ee153f05d23f39a87781cebdbd544c4213eb20b605&meta=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ijg2OGFmMjMzMzMwYTk2ZmFjNTUzMTBhMmQyN2E2MmQ1ZWM1YWY5Zjg3ZDBhOTg5OTNhMzk0MjZlMDg1NGI2NzcifQ.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.q5SdUNnrvSAIvH85ry0wxvt4PrmxEoisaHIfbRXZfGNaTDa-TNiod_p7dHU06Wj77GASV-SPbjkIFkKI9hkSwtXvAn1FrhHAzF0dRdhZS-X0l7HRrOgc58foP2vsTY-MdQSNaClLMM8h0T0zsAndcDsH8QSy7eJ15Wwppkig0TV3q3c9RdvgD0uNAp-LkDRmK3bH6uNb2iLv4m0NiMcjNK75tVm-gHUPWUQo6qRhZ-lFXW_cCc_4Zj2v27rH1Y2uI7EHIsrMMPKXrSC-F4T0UmhNDVN-1iBczTxoIPRjX7Sakb3belAe4185Yi2xlTnuLD6uf8FUT9CjyZNPYnzVbA&redirect_url=%2F via 2606:4700:300a::6813:c31d → 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/castorpb.dev.svg)](https://aaaa.bot/castorpb.dev)

Check again

castorpb.dev Has IPv6

A (IPv4)	172.67.221.226 104.21.70.84
AAAA (IPv6)	2606:4700:3031::6815:4654 2606:4700:3031::ac43:dde2

www.castorpb.dev Has IPv6

A (IPv4)	172.67.221.226 104.21.70.84
AAAA (IPv6)	2606:4700:3031::ac43:dde2 2606:4700:3031::6815:4654

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: castorpb.dev
Measured 2026-11-05 19:16:07 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    172.67.221.226, 104.21.70.84
AAAA (IPv6): 2606:4700:3031::6815:4654, 2606:4700:3031::ac43:dde2
www AAAA:    2606:4700:3031::ac43:dde2, 2606:4700:3031::6815:4654

Readiness grade A: Website, mail and DNS all work over IPv6.
- Website over IPv6: castorpb.dev has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3031::6815:4654: answers (TCP 443)
    2606:4700:3031::ac43:dde2: answers (TCP 443)
- www over IPv6: www.castorpb.dev has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3031::ac43:dde2: answers (TCP 443)
    2606:4700:3031::6815:4654: 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: 2 of 2 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://castorpb.dev/ via 2606:4700:3031::6815:4654 -> HTTP 302, certificate: valid
    https://summer-silence-5c5a.cloudflareaccess.com/cdn-cgi/access/login/castorpb.dev?kid=273aa8d7c518f67bf9a859ee153f05d23f39a87781cebdbd544c4213eb20b605&meta=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6Ijg2OGFmMjMzMzMwYTk2ZmFjNTUzMTBhMmQyN2E2MmQ1ZWM1YWY5Zjg3ZDBhOTg5OTNhMzk0MjZlMDg1NGI2NzcifQ.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.q5SdUNnrvSAIvH85ry0wxvt4PrmxEoisaHIfbRXZfGNaTDa-TNiod_p7dHU06Wj77GASV-SPbjkIFkKI9hkSwtXvAn1FrhHAzF0dRdhZS-X0l7HRrOgc58foP2vsTY-MdQSNaClLMM8h0T0zsAndcDsH8QSy7eJ15Wwppkig0TV3q3c9RdvgD0uNAp-LkDRmK3bH6uNb2iLv4m0NiMcjNK75tVm-gHUPWUQo6qRhZ-lFXW_cCc_4Zj2v27rH1Y2uI7EHIsrMMPKXrSC-F4T0UmhNDVN-1iBczTxoIPRjX7Sakb3belAe4185Yi2xlTnuLD6uf8FUT9CjyZNPYnzVbA&redirect_url=%2F via 2606:4700:300a::6813:c31d -> HTTP 200, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/8g2GYH5RQI

Permanent link: aaaa.bot/r/8g2GYH5RQI · How we measure

Checked 2026-11-05 19:16:07 UTC. Full DNS report: dns.pizza/domain/castorpb.dev · Age, certificate and blocklists: how.is/castorpb.dev · JSON: /api/v1/castorpb.dev