My Mac Book Pro has only 120 GB of operating memory. At about 7 GB of free space, I started getting error messages indicating I couldn't perform operations. The first signal was that I couldn't download a system update.
I'm not an experience Mac user. My first task was to find out how much space I actually had. I hoped to download things I wanted to archive to an external drive. The operation was frequently halted because of my lack of operating space. I went to the System Preferences. In the search function, I wrote "storage."
The search directed me to Apple ID. Under Apple ID is iCloud Storage. The major part of the usage was Photos and Videos. These were all on my computer. Wrongly I assumed that iCloud storage was affecting my system operations. I deleted the iCloud photos. I got a signal that I had a month to download all the photos from iCloud before they were permanently deleted. And now I don't know how to turn back the clock and reverse my mistake. iCloud takes up very little of the space on the actual computer.
So then I went searching further. I was directed to right click on the Macintosh HD in the left column in Finder and open up Get Info. There I found the actual memory I have on my computer.
I searched further and found these instructions. Open the Apple menu, then select About This Mac. Click the Storage tab in the toolbar to see how much disk space you have available.
I looked under Apps and found that the bigger user of space was Box, which I use for work. All my Box documents were present on my computer as well as in the cloud. Since I can access the cloud through a browser, I decided this would be the firs place to attack.
I tried to drag the Box app to the Trash and also right click to delete. A message said Box was open and that I had to quit Box before deleting it.
I was now free to attack the problem another way. Apps were taking up 17.53 GB. Documents in green 13.97 GB. Mail in blue 8.29 GB. Music creation 2.39. Messages 2.01 GB. Podcasts 1.7 GB. System in light grey 11.32 GB. Other in dark grey at 44.7 GB was taking up the most space. I found Other is mostly Cache.