DNS records explained: how to look up A, MX and TXT records

DNS records are the entries that tell the internet where to send traffic for your domain: which server hosts the website, which servers receive email, and which services are allowed to send email for you. To look up a domain's records, you query its DNS for a record type, such as A for the website's address, or a TXT record lookup for verification codes and email rules.

This guide explains the common record types in plain words, how to run a lookup, and the DNS mistakes that most often break websites and email.

What are the main DNS record types?

Each record also has a TTL, the time to live, in seconds. It tells resolvers how long to cache the answer, which is why a change can take a while to reach everyone.

How to do a TXT record lookup

A TXT record lookup asks a domain's DNS for its TXT records. You can do it three ways:

1. On the command line: nslookup -type=TXT example.com on Windows, or dig TXT example.com on macOS and Linux.
2. For a subdomain, look up the full name, such as dig TXT _dmarc.example.com for DMARC.
3. With a DNS checker, which looks up every record type at once and compares the answer from each name server.

TXT records usually hold three kinds of data:

• SPF, starting with v=spf1, which lists the servers allowed to send email for the domain.
• DMARC, at _dmarc.example.com, starting with v=DMARC1, which tells receivers what to do with email that fails checks.
• Verification codes from services such as Google Search Console or email providers.

DKIM keys are also TXT records, at a name like selector._domainkey.example.com, where the selector is set by your email provider.

Why DNS changes take time to show

DNS changes take time because resolvers around the world cache the old answer until its TTL runs out. A record with a TTL of 3600 can stay cached for up to an hour after you change it. People call this propagation.

To make planned changes faster, lower the TTL to a few minutes a day before the change, make the change, then raise it again afterwards. Comparing the answer from each of your name servers shows whether the change has reached all of them.

Common DNS problems and how to fix them

For email, the DMARC overview at dmarc.org explains how SPF, DKIM and DMARC work together.

DNS checklist before a migration

Moving a site or email to a new host is when DNS mistakes happen most. Before you switch:

1. Export every current record from the old provider, including TXT and CAA records that are easy to miss.
2. Lower the TTL of the records you'll change, a day ahead.
3. Recreate the records at the new provider and compare them line by line.
4. Keep the email records (MX, SPF, DKIM, DMARC) exactly as they are unless email is moving too.
5. Switch the name servers or the changed records.
6. Check every name server's answer and test the site and email from outside.
7. Raise the TTL again once everything works.

How DNS affects SEO

DNS doesn't rank pages, but it decides whether search engines can reach them. If DNS fails, crawlers can't connect, and a long outage can cause pages to drop. Slow DNS also adds time to the first visit. Keep DNS with a reliable provider and watch it like any other part of uptime.

Check DNS records with the DNS Checker

The DNS Checker looks up A, AAAA, CNAME, MX, TXT, NS, CAA and SOA records in a few seconds, using public DNS only. It compares the answer from each name server, reads and tests SPF, DMARC and DKIM records for email, shows each record's TTL, and explains what each problem breaks and how to fix it.

If a site won't load at all, the Website Down Checker shows whether the failure is in DNS or further along. Domain and certificate expiry dates are in the SSL Checker.