MacOS is really efficient when using files however over time temporary data such as caches created by third party software can slow you macOS system down. Built right into macOS Sierra is the ability to easily clean things up!
It is advisable to carry out a backup of your Mac first Time Machine is great for this.
Firstly hold down ⇧ shift and start your Mac up, keep holding down shift until you see your usual login screen. While booting and holding down shift you will see a loading bar, usually grey but as I like to be different I have my Mac configured black and white!
It can take a while for this safe boot to complete and for the loading bar to complete to 100% if macOS needs to repair your disk or if large amounts of cache are to be removed, but hey this is step 1 in speeding up your Mac, be patient and wait for it to complete!
Once you reach the login screen you will see the words ‘Safe Boot’ in the menu bar:
Log in to your account, if you are using File Vault you may have to log in twice, I did!
In safe mode or safe boot as the screen tells us only minimal system resources are loaded so a flickering screen is normal, also don’t expect to start surfing the web as you usually would or editing files in PhotoShop!
Next step, go to the Apple Menu then About this Mac:
Then Storage and click on the manage button:
You will be presented with the following screen:
This is a test Mac so it doesn’t have a great deal to tidy up and optimize.
Yes you can access this menu from the Apple Menu > About this Mac , at any time, however by starting in Safe Mode we have prevented third party apps from loading checked the Hard Drive’s integrity and deleted any unnecessary system and kernel caches!
I’m not going to run through every option on this screen but it allows you to easily sift through the GB’s of data you have on your Mac and remove some of the clutter.
Once you are done restart your mac as you usually do , also available in Apple Menu > Restart.
Back up first using Time Machine or similar.
Start in safe mode by holding down ⇧ shift.
Carefully review the options in Apple Menu > About this Mac, Storage > Manage.