The AID decides which application the card runs. Type a prefix (say A000000003) to list every entry for that scheme, or just search by scheme name β the RID part of each AID is highlighted.
| AID (bold part is the RID) | Product / application |
|---|
An AID has two parts: the first 5 bytes are the RID β the scheme's registered identifier, like A000000003 for Visa, A000000004 for Mastercard, A000000333 for UnionPay β followed by the PIX, the scheme's own product extension. Terminals select applications by partial match: a candidate entry may be just the RID, and any card application starting with it counts as a hit. So the first 10 hex characters pin down the scheme; the rest distinguishes the product. On the wire you'll find it inside DE55 as tag 4F (the application the card selected) and tag 84 (DF Name).
Multi-application cards carry more than one AID β a dual-brand card holding a UnionPay application alongside an international scheme's is the classic case. Terminal and card settle on one through application selection (the PSE/PPSE directory plus priority), and the AID that wins decides which network the transaction rides and which fee schedule applies. When the same card goes through UnionPay at merchant A but Visa at merchant B, the first thing to compare is tag 4F in each transaction's DE55.
Visa, Mastercard and Discover each have a "US Common Debit" row above. The background is the US Durbin Amendment: regulation requires every debit card to support at least two unaffiliated networks so merchants can choose the routing. Each scheme therefore issued a shared debit AID next to its own β the global AID routes over the scheme's network, while the common AID lets the merchant route to regional debit networks like PULSE or STAR. Seeing both AIDs on one card in US acquiring is normal, not a misconfiguration.