Live WHOIS/registration data via the RDAP protocol, plus live A/AAAA/MX records over DNS-over-HTTPS. Try github.com, wikipedia.org or bbc.co.uk. The domain you type is sent to Google Public DNS (or to Cloudflare DNS if Google does not answer) and to rdap.org for registration data. Results are held in memory for five minutes so repeat lookups do not re-query.
The record types worth knowing
| Type | Maps | You look at it when… |
|---|---|---|
A |
name → IPv4 address | “the site is down”: does the name even resolve? |
AAAA |
name → IPv6 address | v6 works at home but not at the office (or vice versa) |
CNAME |
name → another name | www points at a CDN and you need to know which |
MX |
domain → mail servers | mail bounces: is it even pointed at the right provider? |
TXT |
domain → arbitrary text | SPF/DKIM/verification records for email and services |
NS |
domain → its name servers | a domain transfer or delegation went sideways |
Learn what you’re seeing
The full resolution story (recursive resolvers, root servers, caching) is in How DNS resolves a name. Also useful: HTTP & TLS and The CLI toolkit (dig and nslookup).
Frequently asked questions
What is a TTL?
Time To Live: how many seconds a resolver may cache an answer before asking again. A 3600 TTL means a change can take up to an hour to be seen everywhere, which is why DNS changes feel slow, and why you lower the TTL before a planned migration.
Why do I get a different answer than someone else?
Caching and geography. Your resolver may hold an older cached record than theirs, and many large sites return different addresses per region (anycast or geo-routing). Both answers are usually correct, just observed from different places at different times.
Is this the same as dig or nslookup?
Same queries, same records, friendlier output. dig and nslookup are the command-line equivalents: worth learning for interviews and servers without a browser. The CLI toolkit lesson walks through both.