Squawk code lookup
Type a transponder code to see what it means, or read the reserved codes below. Three emergency codes are universal. Almost everything else depends on the region.
Four digits, each one 0 to 7.
Worldwide
Reserved by ICAO. These three mean the same thing everywhere.
Hijacking. Controllers will not ask about it directly on frequency; the response happens on the ground.
Lost communications. The aircraft is still flying normally and is expected to follow the lost-comms procedure for its clearance.
Anything from an engine failure to a sick passenger. It gets priority handling and lights up every screen looking at that sector.
United States
Reserved in the US for active air-defence intercepts. Never assigned to ordinary traffic.
The standard code for VFR flight in the United States and Canada, and in Australia outside controlled airspace.
Glider operations not in contact with ATC, United States.
Aircraft working a fire, United States.
SAR aircraft on a mission, United States.
US military and some other operations conducted outside controlled airspace.
Europe
What you squawk in Europe when nobody has assigned you a code. The European equivalent of 1200. This is the single most common mix-up: the two regions chose different codes for the same idea.
The default when no code has been assigned, notably on entering European airspace from an oceanic sector.
Aerobatic and display flying, Europe.
United Kingdom
UK: used where an aircraft is lost or unsure of position and working it out.
UK: operating in the visual circuit at an aerodrome.
Australia
Australia, in controlled airspace. Outside it, Australian VFR uses 1200, so this is not a straight equivalent of the US or European code.
How this works
- Four octal digits, not four decimal
- A transponder sends twelve bits as four groups of three. Each digit runs 0 to 7, so the full code space is 4,096 codes. The digits 8 and 9 never appear in a squawk. A code that looks like a plausible number can be one a transponder physically cannot be set to.
- Only three codes are universal
- ICAO reserves 7500 (unlawful interference), 7600 (lost radio) and 7700 (general emergency) worldwide. Everything else is assigned regionally. The VFR conspicuity code is 1200 in the United States, 7000 across most of Europe, and 1200 or 3000 in Australia depending on the airspace.
- Most codes are discrete assignments
- The majority of the 4,096 codes have no standing meaning. A controller assigns one to a particular aircraft for a particular flight so the radar can tell it apart. The code means nothing before or after that flight. Only the reserved codes carry meaning wherever you see them.
Seen one in a raw message?
A squawk rides in a DF5 or DF21 reply. The four digits are interleaved across the field rather than stored in order. Paste the frame to see the code extracted bit by bit.
Open the ADS-B message decoder