Look up any domain, IP address or mail setup
Registry records, DNS, SPF, DKIM and DMARC, blocklists, TLS and reachability in one place. Free to use, with watches and an API for teams that need more.
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- lookups this week
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- names and addresses seen
- 3,174
- timeline snapshots
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Every check, one Lookup bar
Pick a tool for a guided page, or type straight into the bar above.
Domain & registry
- WHOIS lookupRegistrar, dates, nameservers and status for any domain.
- RDAP lookupThe structured registry record behind WHOIS.
- Domain availabilityIs the name free? Check the registry, then register it.
- Domain TimelineEvery recorded change to a domain: registrar, dates, nameservers, records, certificate.
- Subdomain finderHost names seen in public certificate logs, with a check on which still resolve.
- Registrar directoryFind a registrar by name, IANA ID or Nominet IPS tag.
- SPF record builderBuild a valid SPF record from the services you use.
- DMARC record builderBuild a DMARC record with the right policy, reporting and alignment.
- MTA-STS and TLS-RPT builderMake senders use TLS to reach your mail servers, with reports when they cannot.
- BIMI record builderShow your logo in the inbox once DMARC is at enforcement.
- MX lookupWhich servers receive mail for a domain, and are they healthy?
- SPF checkerValidate SPF and count the DNS lookups before receivers do.
- DKIM checkerFind published DKIM keys and check their strength.
- DMARC checkerPolicy, reporting and alignment in one view.
- Email setup checkMX, SPF, DKIM, DMARC, MTA-STS and a live SMTP test, with a spoofability verdict.
- Header decoderPaste a message header and see the route, delays and authentication results.
- DMARC report analyserUpload aggregate reports and see who sends as your domain and what passes.
- DMARC report monitoringSend your aggregate reports to us and read a dashboard instead of XML.
- Open relay testDoes your mail server accept mail for other domains? Owners only.
- Email address checkerIs this address real? Syntax, mail servers, disposable and role checks, plus a live mailbox probe.
Network & IP
- CIDR calculatorNetwork, range, mask, usable hosts and reverse zone for any prefix.
- Port checkerWhich TCP ports answer from the internet, with service banners.
- PingICMP reachability and latency from London.
- TracerouteThe path packets take from London to a host.
- IP lookupWho holds an address, which network announces it, and what its reverse DNS says.
- AS number lookupName, country and registry for an autonomous system.
Registry data, as published
RDAP first, with legacy WHOIS alongside. Redactions are labelled, never guessed at.
Findings, not just records
Every check explains what was seen, why it matters and how to fix it, with a guide for each finding.
Watch what matters
Uptime, DNS changes, certificate and domain expiry alerts arrive with Pro.