UptimeRobot
uptimerobot.com
Watches your site around the clock and emails you when it stops answering
Free tier
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downforeveryoneorjustme.com
Settles whether a site is actually down or only down for you.
Type a domain, get one sentence back. It fetches the site from their servers, so a failure there means the site is genuinely down and a success means the problem is your network, your DNS or your ISP — which is the fork in the road you need before you start debugging anything. It has been doing this one job since 2008. It is a single request from a single vantage point, so it will not tell you about a regional outage or a slow site that still responds.
Questions
Works the moment the page loads. No account, no email, no trial. One check from one location — it misses regional outages and says nothing about why a site is down.
Yes. Down for Everyone or Just Me sends your input to its own servers to process it. That is fine for public material; for anything containing personal data, use one of the on-device tools instead.
One check from one location — it misses regional outages and says nothing about why a site is down.
Alternatives
Same category or same task, ordered by how closely they overlap.
uptimerobot.com
Watches your site around the clock and emails you when it stops answering
lookup.icann.org
The registry's own WHOIS record for a domain, with no upsell
ipinfo.io
Tells you an IP address's owner, network and approximate location
pagespeed.web.dev
Scores a page on real-user Core Web Vitals and lab measurements
ssllabs.com
Grades a site's TLS configuration from A+ down to F and says why
securityheaders.com
Grades the HTTP security headers a site sends and names the missing ones