Free calculators, cheat sheets, and deep-dive guides built by a working sysadmin. No fluff, no paywalls — just the stuff you actually need on the job.
Browse Tools →Bookmark these. Use them daily. They run entirely in your browser — no data leaves your machine.
CIDR notation, VLSM breakdown, host counts, and visual subnet maps. Supports IPv4 & IPv6.
networkingQuery A, AAAA, MX, CNAME, TXT, and SOA records. Check propagation across global resolvers.
dnsInspect certificate chains, expiration dates, cipher suites, and HSTS headers for any domain.
securityVisual cron schedule builder with plain-English translations and next-5-runs preview.
linuxCryptographically random passwords, SSH keys, and API tokens. Configurable entropy.
securitySearchable database of 6,000+ known ports with service names, protocols, and risk notes.
networking270+ essential one-liners for Linux, Windows, Active Directory, Exchange, Docker, and more. Click to copy.
referenceLive status for AWS, Azure, GCP, M365, GitHub, Cloudflare, Slack, and more. Auto-refreshes every 5 minutes.
cloudLong-form tutorials and reference material written from real-world experience.