Yes — crtr.app has IPv6.

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

IPv6 readiness

Works over IPv6, with one gap: its mail servers lack IPv6.

Website over IPv6 crtr.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3034::6815:5707 answers · 443✓ 2606:4700:3034::ac43:8b1d answers · 443	yes
www over IPv6 www.crtr.app has 2 IPv6 addresses and answers on every one we tested. ✓ 2606:4700:3034::6815:5707 answers · 443✓ 2606:4700:3034::ac43:8b1d answers · 443	yes
Mail servers (MX) have IPv6 None of the mail servers has an AAAA record. eforward1.registrar-servers.com ✗eforward2.registrar-servers.com ✗eforward3.registrar-servers.com ✗eforward4.registrar-servers.com ✗eforward5.registrar-servers.com ✗	no
Nameservers have IPv6 2 of 2 nameservers checked have an AAAA record, so IPv6-only resolvers can look the domain up. maya.ns.cloudflare.com ✓stanley.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://crtr.app/ via 2606:4700:3034::6815:5707 → 302https://crtr.app/site-lock via 2606:4700:3034::6815:5707 → 200

works

What's keeping crtr.app from an A

Mail servers without IPv6
eforward1.registrar-servers.com, eforward2.registrar-servers.com, eforward3.registrar-servers.com, eforward4.registrar-servers.com, eforward5.registrar-servers.com have no AAAA record, so mail from IPv6-only servers can't reach them directly. If a provider runs your mail, that's their setting; if you run it, add AAAA records for these hosts.

Check again

crtr.app Has IPv6

A (IPv4)	104.21.87.7 172.67.139.29
AAAA (IPv6)	2606:4700:3034::6815:5707 2606:4700:3034::ac43:8b1d

www.crtr.app Has IPv6

A (IPv4)	172.67.139.29 104.21.87.7
AAAA (IPv6)	2606:4700:3034::6815:5707 2606:4700:3034::ac43:8b1d

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: crtr.app
Measured 2026-11-03 04:09:19 UTC by aaaa.bot (one server on Fly.io, region iad)

A (IPv4):    104.21.87.7, 172.67.139.29
AAAA (IPv6): 2606:4700:3034::6815:5707, 2606:4700:3034::ac43:8b1d
www AAAA:    2606:4700:3034::6815:5707, 2606:4700:3034::ac43:8b1d

Readiness grade B: Works over IPv6, with one gap: its mail servers lack IPv6.
- Website over IPv6: crtr.app has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3034::6815:5707: answers (TCP 443)
    2606:4700:3034::ac43:8b1d: answers (TCP 443)
- www over IPv6: www.crtr.app has 2 IPv6 addresses and answers on every one we tested.
    2606:4700:3034::6815:5707: answers (TCP 443)
    2606:4700:3034::ac43:8b1d: answers (TCP 443)
- Mail servers (MX) have IPv6: None of the mail servers 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://crtr.app/ via 2606:4700:3034::6815:5707 -> HTTP 302, certificate: valid
    https://crtr.app/site-lock via 2606:4700:3034::6815:5707 -> HTTP 200, certificate: valid
DNS answers via DNS-over-HTTPS (Cloudflare). Method: https://aaaa.bot/method
Permanent link: https://aaaa.bot/r/RtH-3oJhtG

Permanent link: aaaa.bot/r/RtH-3oJhtG · How we measure

Checked 2026-11-03 04:09:19 UTC. Full DNS report: dns.pizza/domain/crtr.app · Age, certificate and blocklists: how.is/crtr.app · JSON: /api/v1/crtr.app