DNS lookup

What DNS does, in plain terms

The Domain Name System is the internet's address book. Computers reach each other using IP addresses, but people remember names, so before your browser can load example.com it first asks a DNS resolver to translate that name into the address of a server. That translation happens in milliseconds, is repeated constantly by every connected device, and is almost invisible — until it breaks, at which point nothing else matters, because no connection can even begin. A DNS lookup tool lets you see exactly what the address book says, rather than what one cached copy of it happens to remember.

The record types this tool queries

An A record maps a name to an IPv4 address, and an AAAA record does the same for IPv6. A CNAME record makes one name an alias of another, so a service can move servers without every customer changing their configuration. MX records name the servers that accept email for a domain, each with a priority number: senders try the lowest number first. NS records declare which nameservers are authoritative for a domain. TXT records carry human- and machine-readable text, most often domain-verification codes and email policies such as SPF and DMARC. Finally, the SOA record describes the zone itself — its primary nameserver, the administrator's contact encoded in a field, a serial number that increments with each edit, and the timers that govern how secondary servers synchronise.

TTL, caching and propagation

Every record carries a time to live, or TTL, measured in seconds. Resolvers may cache an answer for that long, which keeps DNS fast and cheap, but also means changes do not take effect everywhere at once. “Propagation” is not a special internet mechanism; it is simply the world's caches expiring at different times. If you lower a TTL a day before a planned migration, the switch will be noticed quickly. If you change a record whose TTL was 86,400, some users may be sent to the old address for a full day, and no amount of refreshing on your part can hurry someone else's resolver. When this tool shows a TTL counting down across repeated lookups, you are watching a cached answer age in real time.

How this lookup works — and its privacy advantage

Traditionally, DNS queries travel unencrypted, so networks along the path can observe which names a device resolves. This tool instead uses DNS-over-HTTPS (DoH): your browser sends the query as an ordinary HTTPS request to Cloudflare's public resolver, which answers in JSON. The request goes directly from your browser to the resolver — NetTools' server is not involved at all — and intermediaries on your local network cannot read it. The trade-offs are worth knowing: the resolver itself can see the query, and DoH answers may differ slightly from your system resolver's if your provider applies filtering or your organisation runs split-horizon DNS. If a record looks wrong here but everything works on your network, or the reverse, that difference is the clue.

How to use this tool

Type a domain, with or without a subdomain — try both example.com and www.example.com, because they are separate names with separate records — choose a record type, and press Look up. Read the Data column carefully: for MX it shows priority and mail server; for TXT, multiple quoted character strings are joined into the single value they represent. “No answer” usually means that name exists but publishes no record of that type, which is normal for most type-and-name combinations. A CNAME in the results means the name you asked about is an alias, and the resolver has helpfully followed it and returned the target's records too.

Related tools

• What Is My IP? — the address your own connection uses
• SSL Checker — verify the certificate on the server DNS points to
• Port Checker — test whether a resolved host accepts connections
• Subnet Calculator — plan the networks behind the records
• Speed Test — check whether slowness is DNS or throughput