Network & Dev Tools
Free tools for networking and everyday sysadmin work. Each one runs entirely in your browser, so nothing you type is sent to a server.
5free tools
Subnet Calculator Network, broadcast, host range and masks for any IPv4/IPv6 CIDR, plus IP range to CIDR conversion. Open tool → Subnet Cheat Sheet CIDR chart /0 to /32 with subnet masks, wildcards and host counts, plus a mask-to-CIDR converter. Open tool → Chmod Calculator Convert between checkboxes, octal modes like 755 and ls -l strings, and copy the exact chmod command. Open tool → Private IP Ranges Check whether an IP is private, reserved or public, with the RFC 1918 ranges, special-purpose blocks and IP classes. Open tool → Cron Expression Generator Build or paste a crontab schedule, get plain English and the next run times. Open tool →