Game cartridges (and ROMs) often contain "padding." Developers fill empty space on the cartridge with repeating zeros ( 0x00 ) or 0xFF to make the game fit a specific memory size (1GB, 2GB, 4GB). When you compress a game, these trillion repeating zeros take up almost no space mathematically.
Highly compressed 3DS games solve this problem. By stripping away junk data and utilizing advanced file compression, you can shrink your game library significantly, allowing you to fit twice as many titles on your SD card. Why 3DS Games Need Compression 3ds games highly compressed
One of the largest games on the system, requiring a New Nintendo 3DS and taking up roughly 3.6 GB of space. Game cartridges (and ROMs) often contain "padding