Yes — 404buildingnotfound.app has IPv6.

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

IPv6 readiness

Website, mail and DNS all work over IPv6.

Website over IPv6 404buildingnotfound.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3033::ac43:8c0d answers · 443✓ 2606:4700:3037::6815:5ed0 answers · 443	yes
www over IPv6 www.404buildingnotfound.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3037::6815:5ed0 answers · 443✓ 2606:4700:3033::ac43:8c0d 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. khalid.ns.cloudflare.com ✓venus.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://404buildingnotfound.app/ via 2606:4700:3033::ac43:8c0d → 302https://pctechwarecloud.cloudflareaccess.com/cdn-cgi/access/login/404buildingnotfound.app?kid=d967ecb335f9ca16a3f32255596f6b54b4f1402aa7022923a123c8ee90e206eb&meta=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6IjAwMmYxODk3Zjc5NzdkMTc4NWU2YzE0OGY5MjRkY2Q1YTUzYTNjMWI0OWZkYTAyYTk2NTBkZDIyNTAwYTBiMjkifQ.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.DLdoU_KO8SsQTCjCY_BjlGModbylIro9y7oCAr3Zl3QcAvyKzaAxwPZzSqDbVQH33smp-bamIVpN6HDcR1jGjwfHRznEZZibnUHeKg5iw9uvca2RRla3Y_rxeQafuDX_z1YmoGoqJXsCGVxADjCOQjooVw6NJHYCVgxlu0hj1EdRSkM3BzIauMHn3HW0OD1MSUpyp_v-qz2StRTBCU4aUeMMUW7K0EMvE86MPZB43xSrBTiyPa410Y2tAIbxmWxtpszxERzwr7w6W9fqeGqK8_6G0K0amlGkl1jPfJEUrHL9a19n8Gloo20Ks3wvpiNiMe4EzHBTi7Aaj-tEHzqsMA&redirect_url=%2F via 2606:4700:300a::6813:c21d → 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/404buildingnotfound.app.svg)](https://aaaa.bot/404buildingnotfound.app)

Check again

404buildingnotfound.app Has IPv6

A (IPv4)	172.67.140.13 104.21.94.208
AAAA (IPv6)	2606:4700:3033::ac43:8c0d 2606:4700:3037::6815:5ed0

www.404buildingnotfound.app Has IPv6

A (IPv4)	172.67.140.13 104.21.94.208
AAAA (IPv6)	2606:4700:3037::6815:5ed0 2606:4700:3033::ac43:8c0d

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: 404buildingnotfound.app
Measured 2026-11-05 20:09:04 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    172.67.140.13, 104.21.94.208
AAAA (IPv6): 2606:4700:3033::ac43:8c0d, 2606:4700:3037::6815:5ed0
www AAAA:    2606:4700:3037::6815:5ed0, 2606:4700:3033::ac43:8c0d

Readiness grade A: Website, mail and DNS all work over IPv6.
- Website over IPv6: 404buildingnotfound.app has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3033::ac43:8c0d: answers (TCP 443)
    2606:4700:3037::6815:5ed0: answers (TCP 443)
- www over IPv6: www.404buildingnotfound.app has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3037::6815:5ed0: answers (TCP 443)
    2606:4700:3033::ac43:8c0d: 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://404buildingnotfound.app/ via 2606:4700:3033::ac43:8c0d -> HTTP 302, certificate: valid
    https://pctechwarecloud.cloudflareaccess.com/cdn-cgi/access/login/404buildingnotfound.app?kid=d967ecb335f9ca16a3f32255596f6b54b4f1402aa7022923a123c8ee90e206eb&meta=eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImtpZCI6IjAwMmYxODk3Zjc5NzdkMTc4NWU2YzE0OGY5MjRkY2Q1YTUzYTNjMWI0OWZkYTAyYTk2NTBkZDIyNTAwYTBiMjkifQ.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.DLdoU_KO8SsQTCjCY_BjlGModbylIro9y7oCAr3Zl3QcAvyKzaAxwPZzSqDbVQH33smp-bamIVpN6HDcR1jGjwfHRznEZZibnUHeKg5iw9uvca2RRla3Y_rxeQafuDX_z1YmoGoqJXsCGVxADjCOQjooVw6NJHYCVgxlu0hj1EdRSkM3BzIauMHn3HW0OD1MSUpyp_v-qz2StRTBCU4aUeMMUW7K0EMvE86MPZB43xSrBTiyPa410Y2tAIbxmWxtpszxERzwr7w6W9fqeGqK8_6G0K0amlGkl1jPfJEUrHL9a19n8Gloo20Ks3wvpiNiMe4EzHBTi7Aaj-tEHzqsMA&redirect_url=%2F via 2606:4700:300a::6813:c21d -> HTTP 200, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/SjeLd2Xr3d

Permanent link: aaaa.bot/r/SjeLd2Xr3d · How we measure

Checked 2026-11-05 20:09:04 UTC. Full DNS report: dns.pizza/domain/404buildingnotfound.app · Age, certificate and blocklists: how.is/404buildingnotfound.app · JSON: /api/v1/404buildingnotfound.app