The easy DNS lookup tool

The A record maps a domain name to an IPv4 address. When you type a domain in your browser, the A record is what tells it which server to connect to, turning the human-readable name into the numbers computers actually route on. A domain can have several A records for load balancing and redundancy.

The AAAA record is the IPv6 version of the A record. IPv6 addresses are 128-bit instead of IPv4's 32-bit, so there are far more of them to hand out, which matters as the free IPv4 addresses run out. Most sites publish both A and AAAA records so IPv4 and IPv6 clients can each reach them.

A CNAME record points one domain name at another (the canonical name). It saves you from copying A records around when several subdomains should resolve to the same place, so www.example.com can point to example.com. Two catches: a CNAME can't sit alongside other record types on the same name, and your root domain can't be a CNAME.

MX records say which mail servers receive email for your domain. Each one carries a priority number (lower wins) and a mail server hostname. When someone emails you, their server reads your MX records and tries delivery from the highest-priority server on down. Running several gives you a fallback when one server is unreachable.

NS records say which name servers are authoritative for your domain, the ones other resolvers should ask for its records. They hook your domain into the wider DNS hierarchy, forming the chain of delegation from the root servers down to your zone. You'll usually run several for redundancy.

TXT records hold arbitrary text, which is why so many things lean on them: proving you own a domain, email security (SPF, DKIM, and DMARC), search-engine verification, and plenty more. A TXT record is made of one or more strings of up to 255 bytes that get joined together, so the value can run well past 255 bytes. DKIM keys often do.

Every DNS zone has exactly one SOA record, holding the admin details for the zone. It names the primary name server and the zone administrator's email, plus the timing values that tell other servers how to treat the zone: the serial number (bumped on every change), the refresh and retry intervals, the expire time, and the negative-cache TTL (how long to remember a "no such record" answer).

A PTR record does the reverse of an A or AAAA record: it maps an IP address back to a domain name. Mail servers lean on them heavily, and plenty will reject mail from an IP with no matching PTR. They also show up in logging and security tooling. PTR records live in special reverse-DNS zones, usually managed by your ISP or hosting provider rather than in your own zone.

CAA records list which Certificate Authorities are allowed to issue SSL/TLS certificates for your domain. They're a guardrail against a CA you never intended handing out a certificate someone could use to impersonate you. Each record has flags, a tag (like "issue" or "iodef"), and a value. With no CAA records, any CA can issue; add them and only the ones you list can.

SRV records point to a specific service rather than just a host: they carry the hostname and port, plus priority and weight for load balancing. You'll see them for things like VoIP (SIP), chat (XMPP), and Active Directory, and they can drive email client auto-config (IMAP/SMTP) per RFC 6186, though few providers use them for that. The full format is service, protocol, priority, weight, port, and target host.