Unlike a standard ISO, which is a bit-for-bit copy of an optical disc including "junk data" used to fill space, a WBFS file "scrubs" this unnecessary data.

A game like Punch-Out!! shrinks from a 4.37 GB ISO to under 400 MB in WBFS format.

The story of the WBFS archive begins not with piracy, but with a limitation of the Wii hardware itself. The console read proprietary, single-layer (4.7GB) and dual-layer (8.5GB) optical discs. To combat loading times and disc wear, a homebrew solution emerged: the WBFS (Wii Backup File System). This was a stripped-down, highly efficient file system designed specifically to store Wii games on a standard USB hard drive. By formatting a drive to WBFS, users could rip their own discs into unencrypted, playable files, stripping away useless padding and encryption layers. This technical innovation transformed preservation; a fragile, scratchable disc could become an immortal, bit-perfect file on a durable hard drive. The WBFS format was the key that unlocked the Wii’s library, turning a console bound by physical media into a digital repository.