macOS Sierra, system size is 180+ GB! I have a MacBook Pro (Retina, 15-inch, Mid 2014) running macOS Sierra, the Mac started to be slow due to storage.

When I've checked my storage I was shocked, from 250 GB I have, 180 GB was allocated to the System it self!

I've checked my friends storage and found that the System is only 30 GB!

How can I manage this and why do I have that much storage allocated to the System?
Download Diskkeeper and analyze your hard drive.


  OmniDiskSweeper will show you the files on your drive, in descending
  order by size, and letting you decide what to do with them. Delete
  away, but exercise caution.


Omnidiskkeeper will show detail of space usage:

Select System and start cleaning.