yarn global helps us manage global npm packages, which is especially useful for CLI tools. How does it work?

By default, it will create a directory at ~/.config/yarn/global (on OSX and non-root Linux), and if you enter the directory, you will find its structure like this:

├── node_modules
├── package.json
├── yarn-error.log
└── yarn.lock

And in package.json, all global packages are defined as dependencies, just like what you are familiar with in a normal JS/TS project.

In this directory, you can do whatever you would normally do, like yarn add, yarn remove, yarn upgrade, yarn upgrade-interactive, etc.

The key point that makes yarn global different is that it handles the binaries by creating symlinks in the directory you specify with --prefix option. On OSX and non-root Linux, the default prefix is /usr/local, which means the binaries will be symlinked to /usr/local/bin, which is usually in the enviroment variable $PATH. So if you prefer using a custom directory for symlinks, do make sure that the directory is in $PATH.