Optimized Storage in macOS Sierra and later* can save space by storing your content in iCloud and making it available on demand. When storage space is needed, files, photos, movies, email attachments, and other files that you seldom use are stored in iCloud automatically. Each file stays right where you last saved it, and downloads when you open it. Files that you’ve used recently remain on your Mac, along with optimized versions of your photos.

* If you haven't yet upgraded to macOS Sierra or later, learn about other ways to free up storage space.

To do so, click on the Apple icon in the left corner, select the option called About This Mac and when you see a pop-up window, choose the Storage Tab. Wait until Mac calculates all the data and you will be able to easily see what type of files of apps take up the most of your storage.
Download and set up OneDrive Files On-Demand. Download and install OneDrive Files On-Demand for Mac. For new OneDrive accounts on Mac OS Mojave, Files On-Demand is turned on by default when you set up OneDrive. Existing users need to turn on Files On-Demand in OneDrive Preferences.

If you don’t know how to check your disk space use on your Mac, here’s where to look. Options 1 and 2: From the Finder. The Finder gives you a couple ways to see how much free disk space you have.

Find out how much storage is available on your Mac

Choose Apple menu  > About This Mac, then click Storage. Each segment of the bar is an estimate of the storage space used by a category of files. Move your pointer over each segment for more detail.

Click the Manage button to open the Storage Management window, pictured below. This button is available only in macOS Sierra or later.

Manage storage on your Mac

The Storage Management window offers recommendations for optimizing your storage. If some recommendations are already turned on, you will see fewer recommendations.

Store in iCloud

Click the Store in iCloud button, then choose from these options:

Desktop and Documents. Store all files from these two locations in iCloud Drive. When storage space is needed, only the files you recently opened are kept on your Mac, so that you can easily work offline. Files stored only in iCloud show a download icon , which you can double-click to download the original file. Learn more about this feature.
Photos. Store all original, full-resolution photos and videos in iCloud Photos. When storage space is needed, only space-saving (optimized) versions of photos are kept on your Mac. To download the original photo or video, just open it.
Messages. Store all messages and attachments in iCloud. When storage space is needed, only the messages and attachments you recently opened are kept on your Mac. Learn more about Messages in iCloud.

Storing files in iCloud uses the storage space in your iCloud storage plan. If you reach or exceed your iCloud storage limit, you can either buy more iCloud storage or make more iCloud storage available. iCloud storage starts at 50GB for $0.99 (USD) a month, and you can purchase additional storage directly from your Apple device. Learn more about prices in your region.

Optimize Storage

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Click the Optimize button, then choose from these options.

Automatically remove watched movies and TV shows. When storage space is needed, movies or TV shows that you purchased from the iTunes Store and already watched are removed from your Mac. Click the download icon next to a movie or TV show to download it again.
Download only recent attachments. Mail automatically downloads only the attachments that you recently received. You can manually download any attachments at any time by opening the email or attachment, or saving the attachment to your Mac.
Don't automatically download attachments. Mail downloads an attachment only when you open the email or attachment, or save the attachment to your Mac.

Optimizing storage for movies, TV shows, and email attachments doesn't require iCloud storage space.

Empty Trash Automatically

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Empty Trash Automatically permanently deletes files that have been in the Trash for more than 30 days.

Reduce Clutter

Reduce Clutter helps you to identify large files and files you might no longer need. Click the Review Files button, then choose any of the file categories in the sidebar, such as Applications, Documents, Music Creation, or Trash.

You can delete the files in some categories directly from this window. Other categories show the total storage space used by the files in each app. You can then open the app and decide whether to delete files from within it.

Learn how to redownload apps, music, movies, TV shows, and books.

Where to find the settings for each feature

The button for each recommendation in the Storage Management window affects one or more settings in other apps. You can also control those settings directly within each app.

If you're using macOS Catalina, choose Apple menu  > System Preferences, click Apple ID, then select iCloud in the sidebar: Store in iCloud turns on the Optimize Mac Storage setting on the right. Then click Options next to iCloud Drive: Store in iCloud turns on the Desktop & Documents Folders setting. To turn off iCloud Drive entirely, deselect iCloud Drive.
In macOS Mojave or earlier, choose Apple menu > System Preferences, click iCloud, then click Options next to iCloud Drive. Store in iCloud turns on the Desktop & Documents Folders and Optimize Mac Storage settings.
In Photos, choose Photos > Preferences, then click iCloud. Store in iCloud selects iCloud Photos and Optimize Mac Storage.
In Messages, choose Messages > Preferences, then click iMessage. Store in iCloud selects Enable Messages in iCloud.

If you're using macOS Catalina, open the Apple TV app, choose TV > Preferences from the menu bar, then click Files. Optimize Storage selects “Automatically delete watched movies and TV shows.”
In macOS Mojave or earlier, open iTunes, choose iTunes > Preferences from the menu bar, then click Advanced. Optimize Storage selects “Automatically delete watched movies and TV shows.”
In Mail, choose Mail > Preferences from the menu bar, then click Accounts. In the Account Information section on the right, Optimize Storage sets the Download Attachments menu to either Recent or None.

Empty Trash Automatically: From the Finder, choose Finder > Preferences, then click Advanced. Empty Trash Automatically selects “Remove items from the Trash after 30 days.”

Other ways that macOS helps automatically save space

With macOS Sierra or later, your Mac automatically takes these additional steps to save storage space:

Detects duplicate downloads in Safari, keeping only the most recent version of the download
Reminds you to delete used app installers
Removes old fonts, languages, and dictionaries that aren't being used
Clears caches, logs, and other unnecessary data when storage space is needed

How to free up storage space manually

Even without using the Optimized Storage features of Sierra or later, you can take other steps to make more storage space available:

Music, movies, and other media can use a lot of storage space. Learn how to delete music, movies, and TV shows from your device.
Delete other files that you no longer need by moving them to the Trash, then emptying the Trash. The Downloads folder is good place to look for files that you might no longer need.
Move files to an external storage device.
Compress files.
Delete unneeded email: In the Mail app, choose Mailbox > Erase Junk Mail. If you no longer need the email in your Trash mailbox, choose Mailbox > Erase Deleted Items.

Learn more

The Storage pane of About This Mac is the best way to determine the amount of storage space available on your Mac. Disk Utility and other apps might show storage categories such as Not Mounted, VM, Recovery, Other Volumes, Free, or Purgeable. Don'