DNS
DNS records explained: A, AAAA, CNAME, MX and TXT
DNS is the directory layer that tells other systems where to find services for your domain. Most website owners repeatedly encounter the same handful of record types.
A records
An A record maps a hostname to an IPv4 address. If a domain should reach a web server at an IPv4 address, an A record is one common way to make that connection.
AAAA records
An AAAA record maps a hostname to an IPv6 address. Do not publish one merely because the field exists; the destination needs working IPv6 connectivity and the service must be reachable over it.
CNAME records
A CNAME makes one hostname an alias of another hostname. It is useful for names such as www or service-specific subdomains when the destination provider wants you to follow a hostname rather than a fixed IP address.
A CNAME is not interchangeable with every other record type, and DNS providers may use special alias or flattening features at the zone apex.
MX records
MX records identify the mail servers responsible for receiving email for a domain. Their priority values help determine which destination should be attempted first when multiple mail exchangers exist.
TXT records
TXT records can carry verification and policy data. Common examples include SPF data and provider verification tokens. DKIM public keys and DMARC policies also use DNS records under specific names.
TTL and propagation
A TTL tells recursive resolvers how long they may cache a record. Changing an authoritative record does not instantly erase valid cached answers everywhere, which is why old data can remain visible for a period after a DNS change.