It's a hidden folder in my user's application-support folder. It's grown to 40+gb. It's completely filled my hard drive. I don't know what to do. Can I just delete the contents of this folder? I'm running High Sierra 10.13 Beta (17A315i). The problem began in earnest on July 18th. Since then, massive numbers of 2.9mb+ files are being written and not deleted. 32,000 of these things. Ugh.