FIELD GUIDE · Internet & Infrastructure
What Is an Internet Outage? How Outages Are Detected From Space and the Network
How can anyone tell, from the outside, that a whole country just lost the internet?
An internet outage sounds like something you'd only know about from the inside — your own connection dropping. But the internet is a network of networks that constantly announce themselves to each other, and that chatter can be watched from the outside. When a country goes quiet, the silence is measurable.
Three lenses, watching at once
No single measurement is enough on its own, so outage detection triangulates.
BGP routing is the internet's global address book. Every network block ("who lives at these addresses") is continuously announced to the rest of the world so traffic knows where to go. When a country is disconnected — or ordered offline — those announcements can vanish, and monitors around the world see the addresses stop being reachable.
Active probing is exactly what it sounds like: gently pinging a spread of addresses across a country and counting how many answer. When the count collapses, connectivity has dropped.
A network telescope listens rather than asks. A chunk of unused internet address space normally receives a steady background hum of stray traffic from all over the world. When a whole region falls off the internet, its share of that hum disappears — a quiet, passive confirmation that something went dark.
When all three dip together, you have a confident outage signal. That fusion is what the live internet outages layer shows, one dot per affected country, according to IODA.
A detected drop is not a verdict
It's worth being precise about what the dot means. The signal is measuring reachability from the outside, not the lived experience of everyone in the country. A partial drop can mean one big network or one region fell off while the rest stayed up. So the honest label is a detected connectivity drop — strong evidence that something broke and roughly how large, but not, by itself, proof of a total blackout, and never an explanation of the cause.
Knowing the why
The detection signal is deliberately silent on cause — and that gap is where curated outage records come in. Cloudflare's Radar Outage Center tracks verified outages and attaches a likely cause to each one, pieced together from public information: a government shutdown order, a storm or earthquake, a severed cable, a power failure, a technical fault. It's an informed assessment, not a courtroom verdict — but paired with the live signal it turns a red dot into a story: the net went dark here, and this is probably why. You'll find that curated list, recent and ongoing, on the internet outages page alongside the live map.
For the physical side of the same story — the cables a break happens to — switch on the undersea cables underneath, or read how the wired world fits together in the Grid.
Frequently asked questions
What is an internet outage?
An internet outage is a measurable drop in the connectivity of a place — a network, a city, a region or a whole country — where a large share of it stops being reachable from the rest of the internet. It can last minutes or weeks, and it can be total or partial. On a live map, an outage shows up as a place that was online and then, all at once, largely wasn't.
How can you detect an outage from the outside?
You watch the internet's own signals rather than the affected networks themselves. The measurement project IODA (Internet Outage Detection & Analysis, from Georgia Tech) fuses three independent lenses: BGP routing (the internet's global address book — whether a country's network blocks are still being announced as reachable), active probing (quietly pinging addresses across a country to see how many answer), and a network telescope (a passive sensor that normally hears a steady background hum of internet traffic, which goes quiet when a region falls off). When all three dip together, that's a strong outage signal.
Does a detected outage mean a total blackout?
Not necessarily. Detection measures a drop in reachability, not the experience on the ground. A 'significant' drop might mean one large provider or one region fell off while the rest of the country stayed online. The signal is very good at telling you something broke and roughly how big it is, but it can't, by itself, prove that every last connection went dark — which is why a careful map calls it a detected drop, not a confirmed blackout.
What causes internet outages?
The big four are deliberate shutdowns (a government ordering providers offline, often around elections or unrest), physical damage (a cut undersea or terrestrial cable, sometimes several at once), power failures (no electricity means no routers, so a blackout becomes an internet outage), and technical faults or attacks (a misconfiguration, a routing leak or a large denial-of-service). The detection signal shows that connectivity dropped and where — it usually can't tell you which of these caused it.
Why do internet outages and undersea cables belong on the same map?
Because the cables are the physical thing and the outage is what happens when the thing breaks. Most intercontinental traffic runs through a few submarine fibre-optic cables; when one is cut — by an anchor, a landslide or sabotage — countries that depend on it can appear on the outage map minutes later. Seeing the wire and its live health side by side turns an abstract red dot into a story you can follow.
How can anyone tell what caused an outage?
You can't from the connectivity signal alone — a dropped country looks the same whether it was switched off, flooded, or cut. Cause comes from correlating the outage with public information: government announcements, news of storms or earthquakes, reports of cable damage, or an operator's own status page. Cloudflare's Radar Outage Center does exactly this — it publishes verified outages with a likely cause (a government-directed shutdown, severe weather, a cable cut, a power failure, a technical fault) drawn from public sources, always framed as an assessment rather than a certainty.
SEE IT LIVE
Everything in this guide is on one real-time map.