**Custom firmware** ("CFW") is a full software modification to your 3DS, comparable to "administrator access" on a computer. It allows you to do anything that the 3DS is physically capable of doing, rather than being limited by whatever Nintendo allows you to do.
* Modification of games ("ROM hacks") through [LayeredFS](https://github.com/knight-ryu12/godmode9-layeredfs-usage/wiki/Using-Luma3DS'-layeredfs-(Only-version-8.0-and-higher))
* Save data editing, backup, and restore
* Emulation of older consoles, as well as native playback of DS and GBA games
* Installing your physical cartridges for digital use