DNS records explained: A, AAAA, CNAME, MX, TXT, NS and SOA

DNS is the phone book of the internet. It turns your domain name into the addresses of your web and email servers. When a record is missing or wrong, your site or email simply stops working, so it's worth knowing what each one does.

The records that matter

• A record: points the domain to an IPv4 address (your web server). Without it, the site can't be found.
• AAAA record: the same for IPv6.
• CNAME: makes one name an alias of another, for example www pointing to the root domain or to a hosting platform. A name with a CNAME can't have other records.
• MX: lists the servers that receive email for the domain, with priorities (lower number = tried first).
• TXT: free text, used for SPF, DMARC, DKIM and ownership checks (Google, Microsoft).
• NS: the nameservers, meaning which company answers DNS questions for your domain.
• SOA: technical details of the zone, such as the serial number and default timings.

Healthy setup checklist

1. The root domain has an A record (and AAAA if your host supports IPv6).
2. www has an A record or a CNAME to the root or host.
3. At least two nameservers, ideally on different networks.
4. MX records exist if you use email on the domain.
5. One SPF TXT record, plus DMARC. See how to set up SPF, DKIM and DMARC.

Common problems and fixes

• Domain doesn't resolve: check the domain hasn't expired (domain expiry guide) and that the nameservers at your registrar match your DNS provider.
• Site moved but old one still shows: the A record still points to the old IP, or the old TTL hasn't expired yet.
• Email stopped after a website move: the new DNS zone is missing the MX records. Copy them over from the old provider.
• Two SPF records: only one is allowed. Merge them into a single TXT record.

Check your records

The website checker lists your A, AAAA, NS, SOA, CNAME and TXT records and the reverse DNS of your server, so you can compare them with what your host expects.