When a website does not load, DNS is one of the first systems worth checking. DNS translates a human-friendly domain name into the address a browser uses to reach a server. A missing, stale, or incorrect record can make a healthy website appear offline.

The records you will see most often

A and AAAA records

An A record maps a hostname to an IPv4 address. An AAAA record maps it to an IPv6 address. Confirm that these addresses belong to the current hosting provider and that the destination server is configured for the hostname.

CNAME records

A CNAME makes one hostname an alias of another. It is common for subdomains such as www. Follow the alias to its destination and verify that the destination eventually resolves.

MX records

MX records direct email for the domain. They do not normally control the website, but changing nameservers or DNS providers can accidentally remove them. Use an MX record lookup after a DNS migration to protect mail delivery.

TXT records

TXT records are often used for domain verification and email policies such as SPF, DKIM, and DMARC. Quoting and formatting mistakes can make a verification fail even though the record appears present in a dashboard.

A practical troubleshooting sequence

1. Run a DNS lookup for the exact hostname that fails.
2. Confirm that the returned record matches the current host or CDN.
3. Check both the root domain and www; they are separate hostnames.
4. Verify the nameservers at the registrar match the DNS provider you are editing.
5. Check for an unexpected IPv6 record if the site works on some networks but not others.
6. Test the resolved IP with a ping test or relevant connectivity check, while remembering that some servers intentionally block ping traffic.

Why a recent DNS change may look inconsistent

DNS answers are cached according to their Time to Live (TTL). After a record changes, some resolvers can keep the older answer until its cache expires. This is often called propagation, although the practical behavior is many independent caches refreshing at different times.

Lowering the TTL before a planned migration can shorten the period in which old answers remain cached. It does not clear entries that are already cached with a longer TTL.

DNS is only the first hop

A correct record confirms that the hostname points somewhere; it does not guarantee the application is healthy. If DNS resolves correctly, check the destination server, TLS certificate, firewall rules, CDN configuration, and application logs.

Working from DNS outward keeps troubleshooting focused: resolve the name, reach the destination, establish a secure connection, and then inspect the application response.