What does a DNS lookup show?
A DNS lookup shows the records a domain publishes: the addresses it points to (A and AAAA), its mail servers (MX), its name servers (NS), text records such as SPF and verification codes (TXT), and aliases (CNAME). Each record has a TTL: how long resolvers may keep it before asking again.
Type a domain, a hostname such as www.example.com or _dmarc.example.com, an email address (its domain is looked up) or an IP address, which shows its reverse DNS (PTR). "All common records" asks for eleven types at once and shows the ones that exist.
DNS record types
| A, AAAA | The IPv4 and IPv6 addresses a name points to |
|---|---|
| CNAME | An alias: the name's records are read from another name |
| MX | The mail servers that take email for the domain, lowest number first |
| NS | The name servers that hold the domain's records |
| TXT | Text: SPF, DKIM and DMARC for email, and codes that prove ownership to Google, Microsoft and others |
| SOA | The zone's primary server, contact address and timers |
| CAA | Which certificate authorities may issue certificates for the domain |
| SRV | Where a service (SIP, XMPP, Autodiscover) runs: host and port |
| PTR | Reverse DNS: the name an IP address points back to |
| HTTPS, SVCB | How browsers should connect: HTTP/3, Encrypted Client Hello, address hints |
| DS, DNSKEY | DNSSEC: the keys that sign the domain's records |
| TLSA | DANE: which certificate a mail or web server must present |
Why compare two resolvers?
After a change, resolvers keep the old answer until its TTL runs out, so for a while Cloudflare and Google may disagree. Rows that differ are marked. If they still differ long after the TTL, the domain's name servers may disagree with each other, or the name answers differently by location, as content delivery networks do.
The page also reads DNSSEC: when a domain is signed and the answer checks out, Cloudflare marks it as validated. A signed domain that does not validate cannot be resolved at all by validating resolvers, which shows as SERVFAIL.
Who is asked when you look up a name?
Nothing is sent until you press Look up. Then your browser asks Cloudflare's 1.1.1.1 and, with the comparison on, Google Public DNS, both over HTTPS. webdave has no server in between and keeps no record of what you look up. Answers are kept in the page's memory for their TTL (at most five minutes), and the page paces its questions so it never floods either resolver.
Questions
Up to the old record's TTL. A record with a TTL of one hour may be cached for an hour after you change it. Lower the TTL a day before a planned move, and raise it again afterwards.
The name does not exist. It was never created, it was deleted, or the domain expired or lost its name servers. WHOIS lookup shows whether the domain is still registered.
The email health check reads MX, SPF, DMARC, DKIM, MTA-STS and blacklists in one go and says what to fix. MX lookup shows just the mail servers.
Not by webdave: your browser asks the resolvers directly. Cloudflare and Google keep short logs under their own privacy policies. The name stays in the page's link (?q=) so you can share or bookmark a lookup.