Temporary cache files that were never deleted Most of them are files that are left behind by applications, many of which you probably no longer use, and some of which you may have deleted and thought you’d uninstalled. What are the files that I should clean up? That way, not only will you free up space, you will also give your Mac a boost and help it run more smoothly.

And, while there are many things you can do to free up disk space, including using Apple’s own storage management tools, it’s a good idea to start by getting rid of the junk that’s accumulated and that you don’t need.

The most obvious reason is that you're running out of space on your boot disk. In this article, we’ll tell you what these files are and, more importantly, how to clean up your Mac’s hard drive so it runs smoothly again. Your Mac accumulates more files, some temporary, some not so temporary and slowly they take up valuable space and start to impact the performance of your computer. However, over time, as you surf the web and install applications, that begins to change. When you first start up a new Mac it's clean, free from junk files and runs smoothly. Nearly full hard-drives perform 17% slower - that’s calculated by MacWorld in a test.

How to clean up mac hard drive space