Free Tools
Free monitoring tools, no signup
Quick, useful tools for anyone who runs a website. Use them free, no account required. When you are ready to watch your sites around the clock, Sentinel is here.
Instant
Live URL Checker
Check any site's status live from our monitoring network in one click. See DNS, TCP, TLS and time-to-first-byte, no account needed.
Check a URLEstimate
Downtime Cost Calculator
Put a real dollar figure on an outage. Enter your traffic and revenue to see what an hour, or a day, of downtime actually costs.
Calculate costConvert
Uptime SLA Calculator
Translate a "99.9%" promise into real minutes. See how much downtime each SLA tier allows per day, week, month and year.
Open calculator