Upon the initialization of Packer, any externally installed plugin will be automatically
discovered and loaded. 

Packer plugins will usually be located within a plugins sub-directory under Packer's main config directory
[PACKER_CONFIG_DIR](/packer/docs/configure#packer-s-config-directory). If `PACKER_CONFIG_DIR` is
either not set or empty, a default equal to `$HOME/.config/packer/plugins` on UNIX, or `%APPDATA%\packer.d\plugins` 
for Windows, will be used.

Where applicable, some installation processes such as `packer init` may override the plugin loading process. 
Refer to the specific installation guides for any plugin loading overrides.

Packer uses the following process for loading the correct plugin:

1. All directories under the `PACKER_PLUGIN_PATH` environment variable, if `PACKER_PLUGIN_PATH`
is set. The `PACKER_PLUGIN_PATH` takes precedences over all other plugin directories; no other directories will be checked.
1. The directory where `packer` is installed, or the executable directory.
1. The current working directory, where `packer build` is being invoked. (`"."`)
1. The `PACKER_CONFIG_DIR/plugins` directory. `PACKER_CONFIG_DIR` refers to *[Packer's config
directory](/packer/docs/configure#packer-s-config-directory)*, if it could be found.

-> **Note:** The `PACKER_PLUGIN_PATH` environment variable can be set to more that one directories;
for example, ~/custom-dir-1:~/custom-dir-2. Separate directories in the PATH string using a colon (:) on UNIX systems 
and a semicolon (;) on Windows systems. The above example path would be able to find a single or multi-component plugin
in either `~/custom-dir-1/packer/` or `~/custom-dir-2/`.