Uptime Checker
Test whether a site is up the way a monitor would: a request from outside its own infrastructure, plus eleven more signals that decide whether "up" actually holds — TLS, DNS, redirects, domain expiry, mail records, security headers. Enter a URL below; the report lands in your inbox.
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"Up" isn't the same as healthy
A server can accept connections while the certificate is a week from expiring, DNS is serving a stale record, or plain-http visitors never reach the secure site. This check reads those signals in the same pass, so "up" comes with the context that decides whether it stays up.
One check now vs uptime over time
A checker answers "is it up right now." Uptime — the number with the nines — is a property of time, and no single check can measure it. That takes the same test repeated on a schedule from outside, with alerts when the answer changes. That is exactly what a monitor is; this page runs one pass of it for free.
Holter watches this for you: outside-in monitors plus dead-man heartbeats for silent failures. Free plan: 5 monitors, 5-minute checks, no credit card.
Monitor uptime continuously — free