APDU Inspector
Paste a command or response APDU and read it field by field — CLA, INS, P1, P2, Lc, data, Le, and the SW1-SW2 status word with its ISO 7816 meaning. Common EMV commands are recognised by name.
About APDUs
ISO/IEC 7816-4 defines the APDU as the unit of exchange between a smart card and reader. A command APDU always starts with a four-byte header — class, instruction, and two parameters — and may carry a length byte, command data, and an expected-response length. The card answers with a response APDU: optional data followed by the two-byte status word.
Command structure
- CLA — class of instruction (e.g. 00 ISO, 80 proprietary)
- INS — instruction code (e.g. A4 SELECT, B2 READ RECORD, AE GENERATE AC)
- P1, P2 — instruction parameters
- Lc — length of command data, then the data itself
- Le — maximum expected length of response data
Frequently asked questions
What does 9000 mean?
Success with no further qualification. The command completed normally.
What does 61xx or 6Cxx mean?
61xx means the card has more data ready — issue GET RESPONSE with Le set to xx. 6Cxx means your Le was wrong — re-issue the command with Le set to xx.
Debugging a terminal flow?
We do this work daily across EMV certifications and custom apps. See EMV capabilities →