The file is a required encryption key used by applications like TagMo , Amiibot , or Ally to decrypt and write Amiibo data to NFC tags. While individual Amiibo character data is frequently updated, the retail key itself has remained static since its discovery. Essential Files for Amiibo Spoofing
Groups dedicated to NTAG215 burning often pin the latest keyretail.bin in their #resources channels. How to Install the Updated Keys amiibo keyretail bin updated download