[**Homebrew**](https://en.wikipedia.org/wiki/List_of_homebrew_video_games) usually refers to software that is not authorized by Nintendo. It allows you to run homebrew games, tools like save editing and backup, and emulators for various older systems.
In many cases, running homebrew on your device is 100% free using just the Nintendo 3DS Sound app. There are also various other exploits in commercial games and the browser to get homebrew running.
**Custom Firmware** ("CFW") enables you to use more advanced hacks that userland homebrew can't easily do. For instance, signature patches let you install unsigned titles that appear right on your HOME Menu.
boot9strap is the newest and best method of launching Custom Firmware that gives us nearly full control of the system only milliseconds into boot, which is similar to the effect of BootMii for the Wii. It gives us even earlier control than arm9loaderhax did, and, unlike standard sighax, boot9strap uses an NDMA overwrite exploit in order to gain Boot9 code execution. This means that any console running boot9strap is capable of dumping the console unique OTP (`OTP.bin`), the ARM11 bootrom (`boot11.bin`), and the ARM9 bootrom (`boot9.bin`).
The benefits of boot9strap over other Custom Firmware launch methods are numerous, and as such it is recommended to use this guide over any other that relies on outdated software (such as menuhax + rxTools, arm9loaderhax, or even normal sighax).
+ Run many old Nintendo DS flash carts that were blocked long ago or never worked on Nintendo 3DS
+ Safely update to the latest system version without fear of losing access to homebrew
## What do I need to know before starting?
+ **Before beginning the guide, you must know the risks of 3DS hacking: EVERY time you modify your system, there is always the potential for an UNRECOVERABLE brick. They're rare, but still a possibility so make sure you follow ALL directions EXACTLY.**
+ If you have already hacked your 3DS before to get an EmuNAND setup, and would like to move the contents of your previous EmuNAND to your new SysNAND CFW, you should follow all instructions and restore your existing EmuNAND when prompted once you reach [Finalizing Setup](finalizing-setup).
+ If everything goes according to plan, you will lose no data and end up with everything that you started with (games, NNID, saves, etc will be preserved).
+ If you need to format a brand new SD card, you can use [`guiformat`](http://www.ridgecrop.demon.co.uk/index.htm?guiformat.htm) and set to an Allocation Unit Size of 32K.