Cleaning up space on your Mac is generally considered a good thing. Your Mac will run better with more free space on its drive, and you (as well as the system and various apps) can utilize the extra space as needed.

One question you're likely to ask is just How Much Free Space do I Need on my Mac? The answer varies depending on how you use your Mac, but for general use when your free space drops below 15% you're likely to start experiencing a few minor performance issues. Let the amount of free space drop even further, and you can expect to see those annyoing beach balls that tell you your Mac is busy doing something. By the way, those spinning beach ball are often referred to as SPOD.

System Tools Can Help

In recent versions of macOS, there's a screen inside the System Information app called Storage Management that aims to help you keep on top of your Mac's storage. You can find the app inside the Applications folder > Utilities > System Information. Once you open the app, go to (in the menu bar) Window > Storage Management. From there you can get a nice bird's eye view of what is taking up space (you can also empty the trash from here, too).

You can discover how much free space is currently available by right-clicking on a volume (that is, the hard drive) either on the Desktop or in a Finder window sidebar and selecting the Get Info item from the popup menu.

The Get Info window will appear in the top left-hand corner of the display. It sometimes is covered up by other open windows, so if you don’t see it, move a few windows around.

Under the General heading you will see three entries of interest:

  • Capacity: The total space available on the selected volume.
  • Available: The free space currently on the selected volume.
  • Used: The amount of space currently in use.

The available value should be a minimum of 15% of the capacity value. More is better. The Finder makes it easy to keep track of the free space available. Open a new Finder window, go to the View menu and select Show Status Bar. At the bottom of every Finder window you'll see how many items are in the window you are looking at and how much free space is available to you on the entire drive.

The first step is to have a current backup of your Mac's data. This is a precaution to ensure you can return your Mac to the state it was in before you began this process. There is nothing more disheartening then to remove files, improve your Mac's performance, and then discover that work report you need to turn in at the end of the week is gone, a victim of enthusiastic cleanup.

If you don’t have a backup method in place, consider using Time Machine, a backup app that comes with your Mac or a cloning app such as Carbon Copy Cloner or SuperDuper.

Start the cleanup process with the easiest methods first, and move on to ones that may be more difficult to perform.

Empty the Trash - The Mac's trash is actually a folder used to temporarily store files you have deleted. All those files you have moved to the trash haven’t been erased, they are still taking up space on your drive. The idea is that if you made a mistake and need a file you trashed, you can easily retrieve it.

The disadvantage is that it is easy to forget to manually empty the trash resulting in a large number of files taking up space. Emptying the trash will permanently remove all files within the Mac's trash. If you would like to check what is in the trash first, move your cursor to the trash icon in the Mac's Dock, right-click and select Open from the popup menu.

If there are any files you need, you can drag them out of the trash or right click on a file in the trash and select Put Back from the popup menu to move the file back where it came from.

Once you have the trash containing only unwanted items, right-click on the trash icon in the Dock and select Empty Trash from the popup menu.

Automate Emptying the Trash

If you would rather not have to do the two-step trash dance, you can configure your Mac to auto-empty the trash after 30-days.

  1. Open a Finder window or click on the desktop to ensure the Finder is the active app.
  2. Select Preferences from the Finder menu.
  3. Click the Advanced icon in the Finder Preference window, then place a checkmark next to the item labeled Remove items from the Trash after 30 days.
  4. You can close the Finder preferences window. From now on each item you place in the trash will be removed for you after a 30-day period has elapsed.

App Trash - Many Mac apps such as Mail, Photos, iPhotos, have their own trash that is independent of the Mac's trashcan. When you delete an email in Mail or an image in Photos the item is moved to the apps internal trash. Just like the Mac's trash, it isn't gone until you delete the trashes content.

The various apps trashcan allow you to recover an item you deleted should you change your mind. When you manually delete the trash in these apps, you permanently remove the item. To delete the trash, open each app and locate the trash icon in the app's sidebar. Clicking on the trash icon will display the current content of the trash, letting you drag an item out of the trash you wish to keep. Once you determine that you want to permanently remove the trash follow these instructions:

Photos: Select the Recently Deleted item in the Photos sidebar (looks like a trashcan), then click the Delete All button in the preview pane.

Mail: Right-click the Trash icon in Mail's sidebar and select Erase Deleted Items from the popup menu.

Mail: Right-click the Junk icon in Mail's sidebar and select Erase Junk Mail from the popup menu.

Uninstall Applications

If you have any apps you no longer use and don’t think you will use again you should consider uninstalling them to free up space. The Mac makes uninstalling apps somewhat simple, just make sure the app you are removing is not currently running and then drag the app from the /Applications folder to the trash (Don’t forget to empty the trash when you're done).

Before you permanently remove an app a few things to consider:

  • If you purchased the app from the Mac App Store, you can always reinstall the app. Just launch the Mac App Store app, select the Purchase tab. Locate the app in the purchase list, and click the Install button.
  • If you purchased the app from a third-party, make sure you have the app's license before you delete it. In many cases, a license key will be needed if you decide to reinstall it later.
  • If you delete an app you may not be able to reinstall the same version at a later date.

Remove Cache and Temporary Files

Your Mac keeps a large number of cache and temporary files that are hidden away from you. These files help the Mac system and specific apps perform their job. Cache files are used to store information that is often used by the system or specific apps. It is quicker to access this information from a cache file than to have an app have to recalculate the information every time it is needed. Cache files usually stay a manageable size, but occasionally they can grow in size over time

Temporary files are as the name suggests just a temporary way for an app to store information. Generally, the temporary files are removed when the app that creates then is closed, or when your Mac shuts down.

Your Mac usually does a good job of managing the cache and temporary files but once in awhile, a cache or temporary file can grow to unwieldy size. Manually removing these files can be done but using third-party apps such as Tinkertool, Onyx or Cocktail, makes the process much easier. By the way, most of these apps have an option to remove system, user, internet and Application caches. It's a good idea to not remove the system caches.

Mail Attachments

If you have ever received an email that included an attachment such as a PDF, image or word doc, chances are the file is still being stored on your Mac. For some of you this may represent a few megabytes of storage space, but for others who routinely exchange large images, audio or video files, this can quickly account for a gigabyte or two of space.

Deleting the Mail attachments can be a time-consuming process if you try to remove them from within the Mail app. An easier way is to use Spotlight, the Mac's search system and display the folder that contains the attachments directly in the Finder. This way you can go through the attachments fairly quickly and trash the ones you wish to delete.

  1. Open Spotlight by clicking on its icon in the Mac menu bar.
  2. Enter "mail downloads" without the quote marks in the Spotlight search field.
  3. Spotlight will build a list of matches. Give Spotlight a little bit of time, then look for matches in the Folder category.
  4. Double-click the mail downloads match in the folder category and the folder will open in a Finder window.
  5. You will likely find individual files within the folder, as well as folders with names containing a long string of numbers and letters. You should check inside each folder for attachments, as well as any individual files. Because the attachments are likely to be known file types, you can use Quick Look to see the content of the file without opening it in an application.
  6. To Quick Look, an item, select the item and click the space bar.
  7. The item should be displayed in the Quick Look preview window.
  8. To close the Quick Look preview click the space bar again.
  9. Drag any attachment you do not wish to keep to the trash.
  10. Don’t forget to empty the trash once you are done.