Where does npm install the packages?

When you install a package using npm you can perform 2 types of installation:

By default, when you type an npm install command, like:

npm install lodash

the package is installed in the current file tree, under the node_modules subfolder.

As this happens, npm also adds the lodash entry in the dependencies property of the package.json file present in the current folder.

A global installation is performed using the -g flag:

npm install -g lodash

When this happens, npm won't install the package under the local folder, but instead, it will use a global location.

Where, exactly?

The npm root -g command will tell you where that exact location is on your machine.

On macOS or Linux this location could be /usr/local/lib/node_modules. On Windows it could be C:\Users\YOU\AppData\Roaming\npm\node_modules

If you use nvm to manage Node.js versions, however, that location would differ.

I for example use nvm and my packages location was shown as /Users/joe/.nvm/versions/node/v8.9.0/lib/node_modules.