Everything on BIN/IIN lookups — what the issuer identification number is, the 6-to-8-digit expansion, and why a 6-digit prefix is now ambiguous.
The card networks expanded the issuer identifier on a payment card from 6 to 8 digits. For anyone doing BIN/IIN lookups it means a 6-digit prefix is no longer guaranteed to identify a single issuer — you often need 8 digits to disambiguate. Here's the what, the why, and the practical fallout.
In 2013, sitting on a balcony in Playitas, Fuerteventura, I built binlist.net as my first ever Go project — a free HTTP API for looking up the issuer of a credit card from its first six digits. It hit 1 million queries/day by 2015. Thirteen years later it's still free, and its commercial sibling iinlist.com is the one we run the business on.