When the Unity Package Manager downloads package contents and metadata, it stores them in a global cache. This makes re-using and sharing packages more efficient, and allows you to install and update stored packages even when offline. The global cache is read-only to users and installed with Unity starting with version 2017.4.
By default, Unity stores the global cache in a root directory that depends on the operating system (and the user account type on Windows):
| Operating system | Default root directory |
|---|---|
| Windows (non-system user account) | %LOCALAPPDATA%\Unity\cache |
| Windows (system user account) | %ALLUSERSPROFILE%\Unity\cache |
| macOS | $HOME/Library/Unity/cache |
| Linux | $HOME/.config/unity3d/cache |
The Package Manager uses two different shared caches, each serving a different purpose. They are stored in subdirectories under the folder location above:
| Subfolder | Description |
|---|---|
npm |
Stores data obtained from registries using the npm protocol. This includes package metadata and package tarballs. |
packages |
This cache contains the uncompressed contents of package tarballs fetched from a registry. |
Inside each of these subfolders, each registry has its own path so that packages hosted on different registries are not mixed up.
The user account running the Unity Editor process must have full write permissions on the root directory and its contents. Without these permissions, the Package Manager cannot download and save the package metadata and contents in the cache.
You can use two environment variables to override either global cache folder:
UPM_NPM_CACHE_PATH overrides the npm folder path. For example (macOS):
UPM_NPM_CACHE_PATH=/dev/ssd/shared/Unity/cache/npm
UPM_CACHE_PATH overrides the packages folder path. For example (macOS):
UPM_CACHE_PATH=/dev/ssd/shared/Unity/cache/packages
You must restart the Unity Editor and the Hub after changing either of these environment variables for them to take effect.