The library folder is a large cache containing imported assets and other data from the project after import. It is generally always 100% safe to delete the Library folder. As Unity has become more stable, this has become much less necessary than it once was.

Unity provides this tool in C:\Program Files\Unity\Hub\Editor\2020.2.1f1\Editor\Data\Tools which allows you to inspect data in the Library folder.

(AssetDatabase v1. See Library/Artifacts for AssetDatabase v2.)

Contains the serialized, imported data keyed by an asset's GUID. binary2text.exe can be used to dump and view the cached imported data.¹⁾

(AssetDatabase v2. See Library/metadata for AssetDatabase v1.)

During import of an asset, the asset importer is run, which produces some number of Unity serializable assets.

The Library/Artifacts folder stores these post-import generated files for every asset, keyed by the hash of the generated asset.²⁾ These generated assets are also called producedFiles in Unity internal.

You can look up a disk Asset's post-import representation by:

1. Opening the Unity Editor.log
2. Right-click on the asset, 'Reimport'
3. In the resulting import debug output, locate the phrase producedFiles[0].contentHash:
4. The key for that recently imported asset will be at the printed hash.

binary2text.exe can be used to dump and view the post-import asset data in this folder.³⁾