I have a late 2013 13" MBP with a 256 GB SSD and 16 GB RAM. It's been nearly out of space for a very long time. I know I should have backed up and deleted files, but I didn't (long story with buying external HDD that I have not been able to partition properly). Anyhow, the computer is always on the verge of being out of space. Today it went from 1 GB free to suddenly 86 MB free. I got a message that the Messages app could not store incoming messages due to being out of space. I had a lot of chrome tabs open and often quitting Chrome will increase space but it didn't. So I restarted the computer. It must have been using an old sleep image file because after I restarted it tried opening up all the apps I had already closed even though I selected do not re-open windows (and there were no windows open when I restarted it). I checked the size of the user library which had been consistently at 220 GB usage, and it's now at 215 GB usage. Would the system possibly eat some of its own files (delete them) if the computer ran out of space? I have so many files from over so many years that it would be impossible for me to tell what if anything is missing. My back-up system before having this sealed up computer was to take the whole HDD out as my archived backup and put it in an external enclosure and only move back the files I absolutely needed to a newly seated drive. With this sealed in machine I know I need to do a back up to an external HDD but it's been giving me problems—I need to bring it to a friend's house to get it formatted. Anyhow, just wondering if anyone knows in the mean time if it's possible files would have been deleted. It seems like the number of files in my user folder is right (approximately what it was before), but the size of the folder has decreased by 5 GB. Are there invisible caches that could have been deleted from the User folder? Also I am running 10.12.6.