My website doesn't work for some visitors: is it IPv6?

Updated 2026-10-17

Short answer: if your domain has an IPv6 (AAAA) record but the server doesn't actually answer on it, visitors whose network prefers IPv6, including many mobile networks, can fail to load your site while it works fine for you.

How to check it yourself

  1. Look up your domain's records: dig A yourdomain.com and dig AAAA yourdomain.com.
  2. If there's an AAAA record, test it directly: curl -6 -I https://yourdomain.com.
  3. If that fails while curl -4 works, the IPv6 address is broken.
  4. Fix the server's IPv6 setup, or delete the AAAA record until it's fixed.

Why it matters

A growing share of visitors, especially on mobile networks, connect over IPv6 first. If your domain has an IPv6 address (an AAAA record) that doesn't actually serve the site, those visitors get a slow load or a failure while everyone on IPv4, often including you, sees a working site. That makes it one of the hardest problems to reproduce.

Common causes

  • An AAAA record points at an old server or an address the host no longer uses.
  • The server listens on IPv4 only, so the IPv6 address answers nothing.
  • A firewall allows web traffic on IPv4 but blocks it on IPv6.
  • The site moved hosts and only the A record was updated.

What Preventionlabs shows

Every report's DNS section checks whether your site accepts connections over both IPv4 and IPv6, alongside DNSSEC, nameservers, CAA limits, mail servers with no address and dangling records.

Price

First report free, no card needed. Then A$50 a month, up to 10 domains.

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