How to Analyze Disk Space on Mac

This guide shows you how to find out what’s taking up space on your Mac’s internal drive, using the built-in tools that come with macOS. You’ll learn to see large files, app storage, and system data, and then decide what to delete or move. No extra software is needed—everything is already on your Mac.

What You’ll Need

• A Mac running macOS Catalina (10.15) or later for the Storage Management tool. Older versions still have the About This Mac storage bar, but not the full recommendations.
• Administrator access if you plan to delete system-level files or apps (you’ll be prompted for your password).
• About 10 minutes of time, depending on how deep you want to dig.

Step-by-Step

1. Open the Apple menu. Click the Apple logo in the top-left corner of your screen.
2. Select “About This Mac”. This opens a window showing your Mac’s model, chip, memory, and startup disk.
3. Click the “Storage” tab. You’ll see a colored bar that shows how much space is used and how much is free. Each color represents a category like Apps, Documents, Photos, and System Data.
4. Click “Manage…”. This opens the Storage Management window, which gives you more detailed tools and recommendations.
5. Review the Recommendations. The left sidebar shows suggestions like “Optimize Storage” (which removes watched Apple TV shows and movies), “Empty Trash Automatically”, and “Reduce Clutter”. Click each one to see what it does, but don’t enable anything yet—just read.
6. Check each category in the sidebar. Click “Applications” to see a list of apps sorted by size. Click “Documents” to see large files, downloads, and other files. Click “Photos” to see your photo library size. Click “Mail” to see how much space emails and attachments take.
7. Sort by size. In any category, click the “Size” column header to sort from largest to smallest. This immediately shows you the biggest space hogs.
8. Delete or move files. Select a file or app, then click the “-” button at the bottom of the list, or right-click and choose “Move to Trash”. For documents, you can also drag them to an external drive.
9. Check “System Data” (or “Other”). This category is often the biggest mystery. Click it to see a breakdown of what’s included—like caches, logs, and Time Machine snapshots. You can’t delete these directly here, but you’ll learn how in the tips below.
10. Use Finder for a deeper look. If you want to see every file by size, open Finder, press Command + F to open a search window. Set the search to your startup disk (usually “Macintosh HD”), then click the “+” button and add a search condition: “File Size” is “greater than” “1 GB”. This shows all files over 1 GB.
11. Sort the Finder results. Click the “Size” column header to sort largest first. If you don’t see the Size column, press Command + J and check “Size” under “Show Columns”.
12. Empty the Trash. After you’ve moved files to Trash, right-click the Trash icon in the Dock and select “Empty Trash”. This permanently frees the space.

Common Mistakes

• Deleting files you still need. Double-check that a file isn’t an important document or a project you’re still working on. When in doubt, move it to an external drive instead of deleting.
• Ignoring the Trash. Moving files to Trash doesn’t free space until you empty it. The Trash can hold gigabytes of data without you realizing it.
• Deleting system files blindly. The “System Data” category includes essential files. Don’t delete anything there unless you know exactly what it is. Using a third-party cleaner that promises to “clear system junk” can cause problems.
• Not checking Time Machine snapshots. Local Time Machine backups can take up a lot of space. They’re stored in the “System Data” category and are usually managed automatically, but if you’re low on space, you can disable them temporarily (see Troubleshooting).
• Assuming the Storage bar is precise. The categories in About This Mac are estimates. The actual size of a folder can differ, especially for System Data.

Tips

• Use the built-in “Optimize Storage” feature. It automatically removes watched Apple TV shows and movies, and can keep files in iCloud when your disk is full. This is a safe, Apple-approved way to free space.
• Clear caches manually (if you’re comfortable). Open Finder, press Command + Shift + G, and type ~/Library/Caches. You’ll see folders for each app. You can delete the contents of these folders (not the folders themselves) to free space. Some apps will recreate their caches as needed.
• Remove language files from apps. Some apps include many languages you don’t use. You can use a tool like Monolingual (free) to strip them, but be careful—it can break some apps if you remove the wrong language.
• Move your photo library to an external drive. Photos can take up tens of gigabytes. You can hold Option and open Photos to choose a different library location.
• Check for iOS backups. If you back up your iPhone or iPad to your Mac, those backups can be large. Go to Finder, click your device under Locations, then click “Manage Backups” to see and delete old ones.
• Use a visual tool like DaisyDisk (paid) or GrandPerspective (free). These show a treemap of your disk, making it easier to spot huge files and folders at a glance. They are read-only, so you can explore safely.

Troubleshooting

• Storage Management won’t open or hangs. Restart your Mac and try again. If it still hangs, open Activity Monitor (in Applications/Utilities) and check if “storagekitd” is using high CPU. If so, wait a few minutes—it may be indexing.
• “System Data” is huge and you can’t figure out why. Check for Time Machine local snapshots: open Terminal and run tmutil listlocalsnapshots /. If there are many, you can delete them with tmutil deletelocalsnapshots /. Also check for old iOS backups as mentioned above.
• You deleted files but the free space didn’t increase. This is often because the Trash hasn’t been emptied, or because the file is still held open by an app. Empty the Trash, then restart your Mac. If the space still doesn’t show, check if you have a Time Machine snapshot that’s holding the space—run the tmutil command above.
• Finder search doesn’t show file sizes. Make sure you’ve added the “File Size” condition correctly. You can also use the “Other” option in the search criteria to find “File Size” under “Attributes”.
• You can’t delete a file because it’s “in use”. Quit the app that’s using it (check Activity Monitor for the process), then try again. If it’s a system file, you shouldn’t delete it anyway.

Frequently Asked Questions

What is “System Data” on my Mac?

System Data (called “Other” in older macOS versions) includes caches, logs, temporary files, Time Machine local snapshots, and other system-level data. It’s not a single folder—it’s a collection of items that macOS groups together for the Storage bar.

Is it safe to delete files from the Library folder?

Most files in your user Library folder (~/Library) are safe to delete if they’re caches or temporary files. But never delete the Library folder itself, and don’t delete anything in /System/Library unless you’re absolutely sure. When in doubt, leave it alone.

Why does my Mac show less free space than the sum of all files?

macOS uses some space for its own needs, like the recovery partition, APFS snapshots, and metadata. Also, the Storage bar categories are estimates, so they may not add up exactly to the total used space.

Can I move apps to an external drive?

Yes, but not all apps support it. Apps downloaded from the App Store can often be moved by dragging them to the external drive in Finder. However, some apps need to be in the Applications folder to work properly. It’s safer to reinstall the app on the external drive if the option is available.

How often should I clean my disk space?

There’s no set schedule. If you regularly work with large files (video, photos, downloads), you might need to clean monthly. Otherwise, a quick check every few months is enough. The key is to catch problems before your disk is completely full, which can slow down your Mac.

Does emptying the Trash permanently delete files?

Yes, for most users. However, with APFS (the default file system), files may still be recoverable with specialized software until the space is overwritten. If you need to securely erase files, use Finder’s “Secure Empty Trash” option (if available) or a dedicated tool.

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