NES Header Inspector
Read a .nes ROM's header — free, with no upload.
Drop a .nes ROM here, or choose one
Processed on your device — nothing is uploaded.
What is the iNES header?
A 16-byte header at the start of almost every dumped NES ROM, describing its PRG-ROM and CHR-ROM size, mapper chip number, mirroring, and a few other flags emulators need to run it correctly.
What's a mapper number?
The number identifying which extra memory-mapping hardware chip is built into the game cartridge (if any) — different mappers support different amounts of ROM, extra RAM, or special features like extra graphics banking.
Is my ROM uploaded anywhere?
No — the header is read entirely on your device. The file is never sent to a server.