Free tools & live data for people who run things on the internet
SysOSX is a small set of sharp, free tools for site owners, indie developers and small teams. Check a website's health in seconds, watch the dates that quietly take sites offline — certificate expiry, domain expiry — and work out what LLM APIs really cost before the invoice arrives. No sign-up, no clutter: one tool, one answer, one clear next step.
The tools
Website Health Check
One domain in, a full report out: is it online, how fast does it answer, when does the TLS certificate expire, when does the domain itself expire, and what do the DNS records say? The flagship check, and the fastest way to spot an avoidable outage.
Check a domain → 🔒SSL Checker
Inspect any site's TLS certificate: issuer, validity window, days remaining, chain and hostname match, and the protocol in use. An expired certificate is a browser warning and a lost customer — see the countdown before your visitors do.
Check a certificate → 🎓SSL Grader
Beyond the certificate: which TLS versions the server still offers, whether its ciphers give forward secrecy, and whether HSTS is set — graded A+ to F with every deduction explained.
Grade a TLS setup → 🚪Port Scanner
What is listening on the usual ports? Twenty TCP connects from sysosx's server, with open, closed and filtered kept honestly separate — filtered means silence, not closed.
Scan common ports → 🚫DNS Blacklist Checker
Is a mail IP or domain on a spam blacklist? Ten IP lists and three domain lists asked from this server, with errors reported as errors — never as clean results.
Check the lists → ✉️Email Deliverability Check
SPF, DKIM and DMARC read and explained: the records that decide whether your mail is believed, with a real SPF lookup count and findings in fix order.
Check email authentication → 📜Certificate Transparency Search
Every certificate ever logged for a domain, read back from crt.sh on the server — the audit that finds forgotten issuance and certificates nobody requested.
Search the logs → 📅Domain Expiry Checker
Find a domain's registrar, registration date and — most importantly — its expiry date and days remaining, straight from registry data, plus the DNS records that point at it. Lapsed domains get re-registered by strangers fast; know your date.
Check an expiry date → 🔗HTTP Status Chain Checker
Every redirect hop for one URL — statuses, targets, final URL and security headers — traced from sysosx's server, not your browser's cache.
Trace a chain → 🌍DNS Propagation Checker
One question, four answers: Google, Cloudflare, Quad9 and OpenDNS on where a domain points, with TTLs and a consensus verdict.
Check propagation → 🧮LLM API Cost Calculator
Pick up to four models — or compare them all — enter your monthly requests and average tokens per request, and see the monthly bill per model, cheapest first. Peak/off-peak traps and scheduled price rises are surfaced, not buried.
Estimate a bill → 🏆LLM Pricing Leaderboard
Every model we track, in one sortable table: input, output and cached-input prices, context window, a link to the official source and the date each price was last verified. Prices we could not confirm on an official page are badged, never hidden.
See the leaderboard → 🔀Subnet Calculator
Network, broadcast and usable range, wildcard mask and binary breakdown from one IP and prefix — plus a VLSM planner and IPv6 expand/compress, all computed in your browser.
Plan a subnet → 🌐DNS Lookup
A, AAAA, MX, TXT, CNAME, NS and SOA records for any domain via public DNS-over-HTTPS resolvers, with TTLs shown and the answering resolver named.
Look up records → 📋Log Parser & Redactor
Drop in an Apache, Nginx, JSON Lines or syslog file, filter by level and text, redact emails, IPs and tokens, and export clean CSV, JSON or text. Files never leave your browser.
Parse a log → 🎲Test Data Generator
Define fields, pick up to 10,000 rows, and download realistic fake data as CSV, JSON or SQL INSERTs — generated locally, never uploaded.
Generate test data → 📜SSL Certificate Parser
Paste a PEM certificate and read its issuer, subject, covered names, validity and fingerprint locally, plus an optional Certificate Transparency history lookup.
Parse a certificate → 🔍Domain Lookup
Registrar, registration and expiry dates, nameservers and status flags straight from registry RDAP data.
Look up a domain → 📟On-Call Scheduler
List the team, pick a rotation length and start date, and get a fair round-robin on-call calendar for weeks ahead — printable, with a CSV download and a shift count per person.
Build a rotation → 🔑Self-Signed Certificate Generator
Common name, SANs, validity and key size in — PEM certificate and private key out, generated locally in your browser and never uploaded.
Generate a certificate → 🗄️Backup Retention Calculator
Grandfather-father-son retention simulated day by day: how many restore points you keep after 1 month, 6 months, 1 year and 2 years, and the storage they need.
Plan retention → ⏱️SLA Error Budget Calculator
Turn a 99.9% or 99.99% target into allowed downtime in minutes, then enter observed downtime or uptime to see the remaining budget and burn percentage.
Calculate a budget → 🕐Time Zone Meeting Planner
A 24-hour grid of your cities' local times, coloured by work, shoulder and night — the true overlap window, the best compromise when there is none, and DST warnings for clock-change weeks.
Find a fair hour → 📈Capacity Estimator
Requests per second and CPU time per request in — cores, whole servers with N+1 or 2N redundancy, Little's-law concurrency and a 1×–10× growth table out.
Estimate capacity → 🔐.env Parser & Validator
Parse and validate a .env file locally — duplicates, invalid keys, malformed lines and unreferenced variables — with values masked and nothing ever uploaded.
Validate a .env →A check tells you about today. Monitoring tells you in time.
Certificates and domains expire on a schedule you do not control, and sites go down at the worst possible moment. The tools above are one-off snapshots; myeventwatch watches the same signals continuously and alerts you by email, Telegram, webhook and more — weeks before an expiry, minutes after an outage. Every report on SysOSX links straight to a free monitoring setup for the domain you just checked.
From the blog
Hands-on guides from twenty years of running systems — Windows Server and RDS, Linux, TLS, email and DNS — written by a former Microsoft engineer. Start with the ones readers actually search for:
- Resolving “No RDS License Servers Are Available” — the RDS licensing failure, traced and fixed step by step.
- TLS Grades, Earned and Lost — what actually moves a server between A+ and F.
- Why Your Email Lands in Spam — SPF, DKIM, DMARC and blacklist checks, in the order to run them.
- What Open Ports Say About a Server — reading a port scan like an operator, not a scanner.
- 10 Handy Linux Command Tricks — small shell habits that save time every week.
- Automating Ubuntu Server Setup with Ansible — the capstone of our Ubuntu Server series.
Why these tools?
Most outages that hurt small sites are not exotic. They are a certificate nobody renewed, a domain that lapsed over a holiday, a DNS record edited once and never re-checked, or an API bill that doubled because a pricing page changed quietly. Each of those is cheap to detect and expensive to discover late. SysOSX exists to make the detection free and instant — and, where a one-off check is not enough, to hand you over to continuous monitoring that does the watching for you.
The LLM pages follow the same philosophy. Model prices change often, promotional rates expire, and headline numbers hide peak-hour multipliers and scheduled increases. Our calculator and leaderboard show the source and the verification date for every price, flag the ones we have not been able to confirm on an official page, and spell out the footnotes that change the bill. Live data, honestly labelled, beats a confident guess.