Free tools
Small utilities for the jobs that come up every week. Everything runs in your browser (the SSL checker's TLS probe runs on our infrastructure): no signup, no tracking, and the things you look up never touch our servers.
Subnet calculator
CIDR in, everything out: network, broadcast, usable range, netmask and wildcard.
NetworkingVLSM subnet planner
Split a base network into right-sized subnets from a list of host counts.
DNSDNS lookup
A, AAAA, MX, TXT, NS and more over DNS-over-HTTPS, with Google as fallback.
EmailSPF, DKIM and DMARC checker
Grades a domain's email authentication and explains what is missing.
DomainsDomain expiry checker
The registry's authoritative RDAP record: expiry, registrar, status, nameservers.
TLSSSL certificate checker
Expiry with days remaining, issuer, protocol, cipher and covered names.
SecurityPassword generator
Cryptographic randomness with honest crack-time estimates.
SecurityPassword breach checker
Checks the HIBP corpus with k-anonymity; the password never leaves your browser.
LifecycleOS end-of-life checker
End-of-support dates for Windows, Server, Ubuntu, Debian, RHEL and macOS.
SLASLA uptime calculator
What 99.9% actually allows, per day, month and year.
SchedulingCron expression builder
Plain-English explanation and the next five run times for any cron line.
Linuxchmod calculator
Permissions to octal and back, including setuid, setgid and sticky.
Want a tool we have not built yet? Tell us and it goes on the list.