# iBeacon packet structure

After 9 bytes of constant preamble, the Proximity UUID, Major and Minor values are transmitted.

UUID is 16 bytes long, Major and Minor are 2 bytes long. Together they form an ID for your iBeacon. Mobile devices recognize which Beacon they approach on the basis of these values.

Byte offsetDefault valueDescriptionProperties
00x02Data length – 2 bytesconstant preamble
10x01Data type – flagsconstant preamble
20x06LE and BR/EDR flagconstant preamble
30x1aData length – 26 bytesconstant preamble
40xffData type - manufacturer specific dataconstant preamble
50x4cManufacturer dataconstant preamble
60x00Manufacturer dataconstant preamble
70x02Manufacturer dataconstant preamble
80x15Manufacturer dataconstant preamble
90xb5Proximity UUID 1st byteset user UUID
100xb1Proximity UUID 2nd byteset user UUID
110x82Proximity UUID 3rd byteset user UUID
120xc7Proximity UUID 4th byteset user UUID
130xeaProximity UUID 5th byteset user UUID
140xb1Proximity UUID 6th byteset user UUID
150x49Proximity UUID 7th byteset user UUID
160x88Proximity UUID 8th byteset user UUID
170xaaProximity UUID 9th byteset user UUID
180x99Proximity UUID 10th byteset user UUID
190xb5Proximity UUID 11th byteset user UUID
200xc1Proximity UUID 12th byteset user UUID
210x51Proximity UUID 13th byteset user UUID
220x70Proximity UUID 14th byteset user UUID
230x08Proximity UUID 15th byteset user UUID
240xd9Proximity UUID 16th byteset user UUID
25xx*Major 1st byteset major value
26xx*Major 2nd byteset major value
27xx*Minor 1st byteset minor value
28xx*Minor 2nd byteset minor value
290xc6Signal power (calibrated RSSI@1m)signal power value