Created by the Doctor V64 backup device. The bytes are swapped in pairs (e.g., "AB CD" becomes "BA DC"), which was necessary for that specific hardware to function.
To play these files on your PC, Mac, or mobile device, you need an emulator. Here are the top choices as of 2024–2026: z64 rom
Most modern emulators like Project64 or Mupen64Plus can automatically detect and read all three formats. However, keeping your library in .z64 is recommended for the best long-term compatibility. Best Emulators for Z64 ROMs Created by the Doctor V64 backup device