DNS Lookup |
A DNS lookup asks what a domain points to: A and AAAA records give its IP addresses, MX its mail servers, NS its name servers, and TXT its text records such as SPF.
DNS lookup is the process of querying a Domain Name System (DNS) server to retrieve the resource records configured for a domain name. Supported record types include A (IPv4 address), AAAA (IPv6 address), MX (mail exchange), NS (name server), TXT, CNAME (canonical name alias), SRV (service locator), and SPF. Each result includes the record value, name, and TTL — the number of seconds the record may be cached by downstream resolvers, as defined in RFC 1035.
| Protocol | UDP (RFC 1035), 3-second timeout per resolver |
|---|---|
| Record Types | A, AAAA, MX, NS, TXT, CNAME, SRV, SPF, PTR |
| Resolvers | Google 8.8.8.8 · Cloudflare 1.1.1.1 · OpenDNS 208.67.222.222 · Quad9 9.9.9.9 · Yandex 77.88.8.8 · Authoritative DNS |
| Caching | Disabled — every query is live |
| TTL | Returned in seconds (per RFC 1035) |
google.com or mail.example.com. Do not include a protocol (http://) or path.
Each row is one DNS record: its type, its value and its TTL, the number of seconds resolvers may keep it in cache.
Each row in the results table corresponds to one DNS resource record returned by the selected resolver for the queried domain. The columns are defined as follows:
| Column | Meaning | Example |
|---|---|---|
| Type | The DNS record type | A, MX, TXT, CNAME |
| Name | The domain or subdomain the record belongs to | google.com., mail.google.com. |
| Value | The record data — an IP address, hostname, or text string depending on type | 142.250.80.46 / aspmx.l.google.com / v=spf1 include:... |
| TTL (seconds) | How long, in seconds, downstream resolvers may cache this record before re-querying | 300 (5 minutes) / 3600 (1 hour) / 86400 (24 hours) |
The tool sends a live query to the resolver you choose (Google 8.8.8.8, Cloudflare 1.1.1.1, OpenDNS, Quad9) or to the domain’s authoritative name servers. “All records” asks for A, AAAA, CNAME, MX, NS, TXT, SOA and CAA one by one, because the old ANY query is no longer reliable (RFC 8482).
The Domain Name System is a hierarchical, distributed naming system defined in RFC 1034 (concepts and facilities) and RFC 1035 (implementation and specification). When a DNS lookup is performed, a UDP datagram is sent to the selected name server on port 53. The server processes the query and returns the matching resource records, or an error code if no records exist for that type.
Recursive resolvers — such as Google (8.8.8.8), Cloudflare (1.1.1.1), OpenDNS (208.67.222.222), and Quad9 (9.9.9.9) — cache results up to each record's TTL and serve cached answers to reduce load on authoritative servers. Authoritative name servers are the definitive source for a domain's records: they never cache and always return the currently published values.
When Authoritative DNS is selected, this tool performs a two-step resolution. First, it queries Google 8.8.8.8 for the domain's NS records to discover its authoritative name servers. Second, it resolves each name server to its IP address via an A record lookup. Finally, it sends the actual DNS query directly to each discovered authoritative server — replicating the behavior of a cold-cache resolver with no prior knowledge of the domain.
Do it yourself
All major operating systems include command-line DNS tools. The online tool queries from a neutral external resolver — results may differ from your local resolver due to caching.
nslookup google.com
nslookup -q=MX google.com 8.8.8.8
nslookup -q=TXT google.com 1.1.1.1
To query a specific record type, use -q=TYPE (e.g. A, AAAA, MX, NS, TXT, CNAME).
Append an IP address after the domain to specify the resolver.
Resolve-DnsName google.com -Type A
Resolve-DnsName google.com -Type MX -Server 8.8.8.8
Resolve-DnsName google.com -Type TXT -Server 1.1.1.1dig google.com A
dig google.com MX @8.8.8.8
dig google.com TXT @1.1.1.1
dig google.com ANY
dig is the preferred tool for sysadmins and developers — it exposes the full DNS
response including TTL, response flags, and the authority section. On macOS, dig
is pre-installed. On Ubuntu/Debian, install it with apt install dnsutils.
A sysadmin migrating a site from one hosting provider to another needs to confirm that A records have propagated before cutting over application traffic. Running the lookup against both a recursive resolver and Authoritative DNS reveals whether old or new IP addresses are being served — catching propagation gaps before users are affected.
A mail server administrator receives bounce reports citing DNS failures. Querying MX records confirms which mail exchange servers are configured and in what priority order. If the MX record points to a decommissioned server, the cause of delivery failures is immediately visible without accessing the DNS control panel.
A developer setting up Google Workspace on a new domain queries TXT records to confirm that
both the Google site verification token and the SPF record (v=spf1) are correctly
published before enabling email sending. A missing or malformed SPF record causes messages to
fail DMARC alignment and land in spam.