What is Library\Artifacts

what is the folder \Library\Artifacts and is it needed to the avatar or can it be deleted?
I noticed its extremly huge in one project.

I took a snoop in mine, and preview spheres like this are also in there.

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Very useful, but doesn’t need to be backed up. I suspect its why I don’t have to wait 15mins for shader variants every time I build the same avatar.

It can be deleted but when you open your project again it will be recreated
it is very large as it stores all of your assets imported in a format that unity can directly use