MacOS High Sierra Suddenly Bloated by About 40GB I noticed that sometime in the last couple weeks or so my 2015 MacBook Pro's High Sierra bloated by about 40GB. In that time span, I have not installed any new software nor have done anything except browse internet and use basic software. 

Things like this happened in the past, but it was all due to Final Cut Pro storing its caches on the disk. The caches were huge and by deleting them I was always able to clear space. 

However, this time it all appears to show in the System section of the Space Used. Does anyone know how one can determine what caused the bloat and reverse it? I cannot afford to have the system occupy 70GB. It leaves no space to do the work. In the past, the system was 20-30GB.

P.S. Having recently looked at the newer MacBook Pros, I was amazed that Apple still sells 128, 256, and 512GB with a straight face. I considered it somewhat low in 2015 when I bought this Mac, but was willing to buy it because I had a desktop as well. However, three years later they still have not improved or increased storage??? All they have done is added a nonsensical touch-bar, removed the actually useful magnet from the charging cord and eliminated the wonderfully glowing apple from the back of the screen. Am I the only one who is astonished by this?
I would recommend an app like OmniDiskSweeper https://www.omnigroup.com/more to help you. Have it search the entire drive, not just your home directory.