free tools for developers and SREs.
Small, fast calculators and generators, no sign-up. We built them for our own work watching uptime and kept them free for yours.
Uptime SLA & Downtime Calculator
Turn an uptime percentage into allowed downtime per day, week, month and year. A free SLA and SLO calculator with the full nines reference table.
Cron Expression Generator & Parser
Build and read cron expressions in plain English, with the next run times and a reference table of the most common schedules. Free, no sign-up.
Error Budget & Burn Rate Calculator
Turn an SLO target and your measured availability into error budget spent, budget left and burn rate, with a burn-rate reference table. Free, no sign-up.
Incident Update Message Generator
Write clear investigating, identified, monitoring, resolved and maintenance messages for your status page. Free, private and generated in your browser.
DNS Lookup: Compare Two Resolvers Side by Side
Check A, MX, NS, TXT and CAA records against Cloudflare and Google at once and see where they disagree. Free, no sign-up, runs in your browser.
HTTP Header & Redirect Chain Checker
See every redirect hop, the final status code and the response headers a URL returns, the way an uptime monitor sees them. Free, no sign-up.
SSL Certificate Checker: Expiry and Chain
Read any public host's TLS certificate: days until expiry, who issued it, which names it covers and whether the chain is complete. Free, no sign-up.
Domain Expiry Checker: Date and Registrar
Check a domain's registration expiry date, days remaining and registrar using public RDAP data. Free, no sign-up. Set up monitoring before renewal is due.
Watch the things these tools measure.
Uptimepage checks your endpoints every minute, opens an incident the moment one fails, and shows the record on a public status page. Start free, no card.