Free network diagnostics

DNS and IP tools for people who run the internet.

Check IP ownership, blocklists and reachability, then inspect a domain's Whois, nameservers, MX, DMARC, DKIM and SPF. Fast and free, with no sign-up.

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IP Tools

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What Is My IP?

Your public IP, browser, location and reverse DNS name.

IP Whois

Who owns an IP address: network, organization, abuse contact.

Email Blacklist Check

Is a mail server IP listed on 20 major spam blocklists?

Ping Check

Send 4 pings to a host and see latency and TTL.

DNS Tools

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Whois Search

Domain registrar, dates, status and nameservers.

Nameserver Lookup

NS records and the DNS provider hosting a domain.

Email Record Lookup

MX, DMARC, DKIM and SPF records in one report.

SPF Validation

Is an IP or CIDR range authorized by a domain's SPF?

DNS Name Lookup

Query A, AAAA, BIMI, CNAME, DMARC, MX, SOA or TXT records.
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Built for administrators

DNS Toolbox answers the questions that come up when email bounces, a site won't resolve, or a new IP block goes live: who owns this address, is it blocklisted, is it reachable, which nameservers and DNS provider host this zone, and is this server allowed to send mail for the domain.

Lookups use public resolvers and the official registry RDAP services. The SPF validator implements RFC 7208 in full and can test an entire CIDR range in one pass, showing exactly which sub-ranges pass and which mechanism authorized them.