EXPLAINER
What is ADS-B?
The open radio protocol behind every flight tracker on Earth. How aircraft broadcast their position to the world — and why the whole system is public by design.
The name says everything
Automatic: it runs without the pilot doing anything. Once the transponder is on, the aircraft reports itself continuously.
Dependent: it depends on the aircraft's own navigation — GPS — rather than on ground radar measuring it from below.
Surveillance: air traffic control uses it to keep aircraft safely separated, alongside (and increasingly instead of) traditional radar.
Broadcast: the data goes out in the open, for anyone within radio range to receive — other aircraft, ground stations, and the enthusiast receiver on someone's rooftop.
From transponder to your screen
The aircraft knows where it is
A GPS receiver on the aircraft computes its exact position, altitude and velocity — many times per second, with no ground equipment needed.
The transponder shouts it out
An ADS-B transponder broadcasts that data over the air, unencrypted, roughly twice a second: callsign, position, altitude, speed, heading and intent.
Receivers listen
A global network of ground receivers — many run by volunteers and enthusiasts — picks up the broadcasts and forwards them to aggregation services.
The map draws the sky
WorldEye plots those reports as live aircraft on the 3D globe. The whole chain from transponder to your screen takes seconds.
Why it's public
ADS-B was built for collision avoidance. For it to work, every aircraft needs to hear every other aircraft nearby — which means the signal can't be encrypted or restricted. The moment you make the broadcast receivable by all aircraft, you've made it receivable by everyone.
So the data was never really "leaked" — it was born open. Receiver networks simply do what any aircraft could do: listen, collect, and share. Flight trackers are downstream beneficiaries of a safety system that had to be public to function.
The limitations
Not every aircraft broadcasts
Most commercial aircraft carry ADS-B, but some older aircraft use only the older Mode S transponder (no GPS position broadcast), and military or sensitive flights may not broadcast at all or be filtered from public feeds.
Coverage is receiver-dependent
A broadcast can only be plotted if a receiver heard it. Oceans, deserts and polar regions have sparser ground coverage — satellite-based ADS-B reception fills many of the gaps, but the map is densest over land.
It's not radar
Classic radar bounces signals off aircraft; ADS-B relies on the aircraft reporting its own position. If the GPS or transponder fails, that aircraft simply goes quiet on the map.
Broadcasts can be absent or spoofed
Because the signal is unencrypted and the system is cooperative, aircraft can disable transponders, and researchers have demonstrated spoofed broadcasts. For navigation and safety it's fine; for forensics, treat it as a signal, not proof.
ADS-B FAQ
What does ADS-B stand for?
Automatic Dependent Surveillance–Broadcast. Automatic — it works without pilot input. Dependent — it depends on the aircraft's own navigation source (GPS). Surveillance — air traffic control uses it to watch traffic. Broadcast — the data is transmitted openly for anyone to receive.
Why is flight tracking data public?
Because ADS-B broadcasts are unencrypted radio signals anyone can receive — they were designed that way so any aircraft or ground station in range can use them for collision awareness. Receiver networks aggregate those public signals into the live feeds every flight tracker uses.
Can ADS-B track military aircraft?
Sometimes. Many military aircraft carry ADS-B transponders and show up like any other traffic when they broadcast. Others operate with transponders off, use encrypted military-only systems, or are filtered out of public feeds before they reach sites like WorldEye.
Is ADS-B the same as the data air traffic control uses?
It's the same broadcast — controllers increasingly rely on ADS-B alongside radar. But controllers see the raw, regulated feed; public trackers see aggregated, sometimes delayed or filtered versions of it.
Can I receive ADS-B signals myself?
Yes, and it's a popular hobby. A software-defined radio dongle and a small antenna are enough to pick up aircraft broadcasts from over the horizon, and many enthusiasts feed their receivers into the same networks that power public flight trackers.
Now go watch it work
Thousands of ADS-B broadcasts, live on one globe. Free forever, no account.
Open the live flight trackerCurious about the ocean equivalent? Read what AIS is
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