Free tools: Network and web
security tools.
Calculate subnets, look up who runs an IP address, query DNS records, convert bandwidth to packet rates and size tunnel MTUs. Free, no sign-up, nothing stored.
- 5
- Free tools
- 0
- Sign-ups needed
- IPv4 + IPv6
- Address families
- 8 s
- Longest check
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Subnet calculator
Network, broadcast, host range and netmask for any IPv4 CIDR block, with a /8 to /32 reference table.IP & ASN lookup
Which network (ASN), organisation and country an IPv4 or IPv6 address belongs to, starting with yours.DNS lookup
A, AAAA, CNAME, MX, NS, TXT, CAA and SOA records for any domain, straight from public resolvers.Bandwidth to PPS calculator
Bit rate to packets per second and back for any frame size, with line-rate overhead and a 95th percentile calculator.Tunnel MTU & MSS calculator
Stack GRE, WireGuard, VXLAN, IPIP, PPPoE or IPsec and get the tunnel MTU, both MSS values and ready-to-paste clamp rules.Yes. There is no sign-up, no limit beyond a fair-use rate limit per visitor, and no upsell inside the tools. They exist because we use the same checks every day and they are useful to anyone who runs a website.
No. Domains, URLs and addresses you enter are used to answer the request and are not stored. The subnet, bandwidth and tunnel MTU calculators do not even send them: they run entirely in your browser.
Yes. After a check the address bar holds the domain or address you checked, so the link opens the same check again. You are welcome to link to any tool page from documentation or articles.
Private, loopback, carrier-grade NAT and other reserved addresses are recognised and labelled, but they are not routed on the public internet, so no network owner, ASN or country exists for them.
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