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Glossary · A record

DNS A Record

A DNS record that maps a hostname like www.example.com to a single IPv4 address so clients know where to send traffic.

Sitecheck Team

An A record maps a hostname such as www.example.com to an IPv4 address. It tells a browser which server to connect to when a user visits your site. A hostname can have several A records; resolvers return all of them and clients pick one.

Why it matters

If an A record points at the wrong or stale IP, traffic goes to a dead server, the wrong tenant, or a parking page. That shows up as failed uptime checks and outages from a user's perspective. Multiple A records can spread traffic across servers for basic redundancy, but they are not a substitute for a real load balancer, since clients keep using whatever IP they cached.

How to check

  • Run dig +short example.com A and confirm every returned IP is one you operate.
  • Set the TTL low (300–600s) before planned IP changes and raise it once stable.
  • Publish an AAAA record alongside so IPv6 clients are not forced to fall back.
  • For subdomains on third-party platforms, prefer a CNAME so the provider can change IPs without your involvement.
  • Test from multiple resolvers and regions; ISP caches can serve old answers long after a change.
  • Keep an audit list mapping each record to the service it serves so retired servers do not linger.

See also