Almost every flight tracker you have used runs on ADS-B. A plane broadcasts its position, altitude, and identity a few times a second, and a network of receivers turns that into the dot you watch cross the map. It is fast, it is everywhere, and it is why live tracking exists at all.
ACARS is the other half. Instead of broadcasting position, it carries the messages between the aircraft and its airline: diversions, emergencies, weather, fuel, and plain text. ADS-B shows you the plane. ACARS shows you what the plane is dealing with.
Side by side
Why you want both
On their own, each tells half the story. A dot holding over an airport is just a dot until an ACARS message shows the crew asking for a new runway. That is the gap Flight Deck closes: it puts the position and the messages in one place, so a delay or a diversion makes sense the moment it starts.
New to the topic? Start with what ACARS is, then see what pilots actually send.
See position and messages together
Flight Deck pairs live tracking with decoded ACARS for any flight. Free on the App Store.
Download Flight Deck