Independently from the specific OS, make sure that the `gcc`, `g++`, `make`, `git`, and `libpng-dev` packages or their equivalents are installed and accessible to the development tools that are used by the project (this means that, for example, on Windows, the packages have to be installed in the WSL environment). The package names and installation methods may vary with each OS.
Install the devkitARM toolchain of devkitPro as per [the instructions on their wiki](https://devkitpro.org/wiki/devkitPro_pacman). On Windows, follow the Linux instructions inside WSL as any steps about the Windows installer do not apply.
**Debian-based distro users:** This applies to Debian, Ubuntu, and similar distros, including in WSL. If necessary, install the `libarchive13`, `pkg-config`, and `gdebi-core` packages to be able to install devkitPro.
**Windows 10 users:** WSL 2 is available in the 1903 release (build 18362) and later, therefore existing WSL 1 and [prerelease WSL](https://docs.microsoft.com/windows/wsl/install-legacy) users are recommended to update. Right-click the Start button or press `Win`+`X`, choose Run, and run `ms-settings:about` to determine the Windows version. Also check Windows Update to make sure your installation is up-to-date.
**Windows 7 and 8.1 users:** pret is no longer focusing on support in pokeemerald for [old versions of Windows](https://support.microsoft.com/help/13853) so consider upgrading to a current release of Windows 10 or try a third-party guide like [this one](https://www.pokecommunity.com/showthread.php?t=425246) instead.
**Windows users:** Consider adding exceptions for the `pokeemerald` and `agbcc` folders in Windows Security using [these instructions](https://support.microsoft.com/help/4028485). This prevents Microsoft Defender from scanning them which might improve performance while building.
**macOS users:** If the base tools are not found in new Terminal sessions after the first successful build, run `echo "if [ -f ~/.bashrc ]; then . ~/.bashrc; fi" >> ~/.bash_profile` once to prevent the issue from occurring again. Verify that the `devkitarm-rules` package is installed as well; if not, install it by running `sudo dkp-pacman -S devkitarm-rules`.
See [the GNU docs](https://www.gnu.org/software/make/manual/html_node/Parallel.html) and [this Stack Exchange thread](https://unix.stackexchange.com/questions/208568) for more information.
`nproc` is not available on macOS. The alternative is `sysctl -n hw.ncpu` ([relevant Stack Overflow thread](https://stackoverflow.com/questions/1715580)).
To build using a toolchain other than devkitARM, override the `TOOLCHAIN` environment variable with the path to your toolchain, which must contain the subdirectory `bin`.