🆔 ICAO Hex Decoder

Decode any 6-character ICAO Mode-S address to country of registration. Offline + instant.

Decodes the country block from the 24-bit ICAO Mode-S address. Pure offline lookup against the ICAO Annex 10 country allocations.

ICAO 24-bit Mode-S hex decoder

Decode any ICAO 24-bit Mode-S address to its country of registration. The decoder bundles 190 country/region allocations from ICAO Annex 10. Lookup is offline and instant.

For OSINT investigations: the country block is the first piece of information about an aircraft. A hex starting with A0–AF is US-registered, 7C–7F is Australian, 78–7B is Chinese, 100000–1FFFFF is Russian. Once you know the country, you can pivot to the country's registry (FAA, CASA, EASA, etc.) for the full record.

For full enrichment with operator, type, photo, and live position, use the Aircraft Enrichment tool which combines this lookup with ADSBdb and ADSB.lol.

Frequently asked questions

What is an ICAO 24-bit address?
A unique identifier transmitted by Mode-S and ADS-B transponders on every aircraft. Assigned by the country of registration from a block ICAO has allocated to that country. The address stays with the airframe — if the aircraft re-registers in another country, it gets a new hex.
How do I read the country block?
Each country gets a contiguous range of 24-bit values. The US has the largest block (A00000–AFFFFF, ~1M addresses, matching the size of the FAA registry). Smaller countries get tighter ranges — Iceland is 4CC000–4CCFFF (4096 addresses). The decoder above shows which range your hex falls into.
How is the hex related to the tail registration?
Most countries don't encode the registration in the hex — there's a registry table mapping hex to N-number. The US is the exception: N-numbers and hex are mathematically convertible (FAA documents the algorithm). Tools like the Aircraft Enrichment page handle this lookup for you.
What does "F0xxxx" mean?
The F0xxxx range is reserved by ICAO for temporary or special use — flight test aircraft, anonymised flights (privacy ICAO addresses), and certain operational categories. Often used for high-profile flights that don't want to be tracked by name; the hex still transmits but doesn't resolve to a registry.
Can I tell if it's a military aircraft?
Country block alone doesn't tell you. Each country has internal sub-allocations for military vs civil that aren't public. The volunteer-maintained tar1090-db aggregates known military hex blocks across countries. The Aircraft Enrichment tool flags these.

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