Every other site that answers “is it down” answers from a monitoring server in a datacentre. That tells you whether the site is up for the datacentre. This page runs the test in the browser you are reading it in, over the connection you are actually using — so when the answer differs from everyone else’s, the difference is the useful part.
For each of the 83 hostnames below, in order:
dns.google/resolve) for the A record. The
address printed next to each site is the resolver’s answer,
not a stored one — a host that has just moved shows its new
address here.HEAD request from
your browser to https://<site>/, timed with the
browser’s own clock from just before the call to the moment the
answer settles. The number therefore covers DNS, TCP, TLS and the
round trip — everything the browser had to do.The request is sent in no-cors mode, which is the
only way a page may contact a site that has not invited it. The response comes
back opaque: the browser hands this page the timing but not the status code. So
a site that answers is reported as answered — not as
“up”, and not as “200”. That is a real limit of doing
this in a browser, and it is the honest way to report it.
Nothing on this page is weighted, smoothed or estimated. The percentage is the count that answered over 83. The average covers only the sites that answered, because a site that never answered has no time to average. Nothing you run here is sent anywhere: the requests go from your browser straight to the sites, and no result is recorded by this site.
A word on the word “continents”. The groups below say where
each service is mainly used — not where its company is registered, and
not where the reply physically came from. Nearly every hostname here sits behind a
CDN, so the answer you are timing most likely came from an edge a few hops from you,
not from the continent in the heading. Reading these timings as six continents’
worth of distance would claim more than the measurement supports: what is actually
measured is your browser reaching 83 named services, most of them at a nearby edge.
Three entries filed under Europe on the used-here rule — adobe.com,
zoom.us and teams.microsoft.com — are US companies;
that is the grouping rule at work, not a slip. Four Mexican sites that had been filed
under South America are now where they belong, under North America.
A site can be perfectly healthy and still fail here — a DNS server that has not caught up, a filter on the network you are on, a peering problem between your provider and theirs, a captive portal in a hotel. All of those are reasons a page might be down for you while every status board says it is fine. Equally, a site can answer here and still be broken: an answer proves something replied, not that it replied correctly. The sweep reports what your connection got, and nothing more.