How to clean junk files from Mac without software (for free)? You can follow it to free up more space on your Macintosh HD. Well, this tutorial gives efficient and easy-to-operate ways to help you clean junk files on your Mac/MacBook. To optimize your Mac performance and keep it in the best state, you need to remove these junk files. That is why your Mac gradually runs slowly or sometimes freezes. The accumulated junk files on your Mac take up more and more storage space on your Mac hard drive.