PIX

PIX

The Proprietary Application Identifier Extension (PIXPIXProtocolApplication-specific AID suffix.Click to view →) is the variable-length suffix of an AID that follows the five-byte RID. While the RIDRIDProtocolFirst 5 bytes of AID identifying provider.Click to view → identifies the application provider, the PIX (0 to 11 bytes) identifies the specific application, product variant, or version within that provider's namespace. Together, RID + PIX form the complete AIDAIDProtocolUnique identifier for card applications.Click to view → used to select applications on a smart card.

PIX Encoding

The PIX format is entirely defined by the application provider — ISO 7816 Part 5 does not mandate a specific structure. In practice, organizations use the PIX bytes to encode:

• Application type (credit, debit, prepaid, loyalty)
• Product variant (domestic vs international, consumer vs commercial)
• Version number (iteration of the application specification)

For example, Visa uses the following PIX conventions under RID A000000003:

PIX in EMV Payment Selection

During an EMV contactless transaction, the terminal first selects the PPSE (AID 2PAY.SYS.DDF01) to discover which payment applications are available. The PPSE returns a list of AIDs. The terminal matches these against its supported AID list, using both the RID and PIX to determine priority and compatibility. Different PIX values may indicate different cardholder verification methods or risk management rules.

PIX in Telecom

SIM card applications also rely on PIX to distinguish telecom applets. The GSMA RID A000000087 combined with specific PIX values identifies USIM, ISIMISIMApplicationSIMSIMApplicationSmart card for mobile network authentication.Click to view → integrated into device SoC.Click to view →, and other telecom file structures. The eSIM provisioning infrastructure uses the GSMA RSPRSPApplicationOver-the-air SIM profile management.Click to view → RID A000000089 with PIX codes that identify the ISD-R, ECASD, and profile management applets on the eUICC.

Selecting by Partial AID

Because the PIX is optional, a reader can send a SELECT APDU containing only the RID (5 bytes). The card will match the first application whose AID begins with that RID. This partial matching allows terminals to discover applications without knowing the exact PIX, useful for cards that may carry multiple versions or variants from the same provider.