What's Taking Up Space on My Mac? Quick Storage Analysis Guide

“Your disk is almost full.”

You’ve seen this notification too many times. You delete a few files. The warning goes away for a week. Then it’s back.

Your Mac says you have 500 GB of storage. You have 3 GB left. What’s eating the other 497 GB?

Here’s how to find out—and reclaim your space.

Why Mac Storage Fills Up Mysteriously

Common culprits:

System Data — Cached files, app data, iOS backups (10-100+ GB)
Photos/Videos — Original quality photos from iCloud (50-200+ GB)
Developer files — Xcode derived data, npm cache, Docker images (20-100+ GB)
Downloads folder — Old installers, archives you forgot about (5-50 GB)
Time Machine snapshots — Local backups eating disk space (10-50 GB)
Mail attachments — Years of email attachments downloaded locally (5-30 GB)
Application caches — Browser cache, Spotify cache, etc. (10-50 GB)

The problem: macOS shows categories (System, Applications, Documents), but doesn’t tell you specifically which files or folders are using space.

Example: “System Data” shows 150 GB. Is it iOS backups? Caches? Logs? You don’t know without digging.

Lesson: Built-in tools show what is using space, not where or how to fix it.

Built-in Method 1: Storage Management

macOS includes a basic storage analyzer. Here’s how to use it:

Step 1: Open Storage Management

Click the Apple menu → System Settings (or System Preferences)
Click General → Storage (or just Storage on older macOS)
Wait for the bar chart to load (30-60 seconds)

Step 2: Understand the Categories

What you’ll see:

System Data — macOS system files, caches, logs, iOS backups
Documents — Files in Desktop, Documents, Downloads
Applications — Installed apps
Photos — Photos library (iCloud originals if downloaded)
Music, Movies, TV — iTunes/Music library, Apple TV downloads
Mail — Mailbox data and attachments
iCloud Drive — Locally synced iCloud files
Messages — iMessage attachments and media
Other Users — Other macOS accounts on this Mac

The problem with categories:

“System Data” is a black box — Could be 5 GB or 150 GB. No breakdown.
No file-level detail — You see “Documents: 80 GB” but not which documents.
No visual treemap — Hard to understand what’s using the most space.

Step 3: Use Built-in Recommendations

Click “i” next to each category for Apple’s suggestions:

System Data:

Remove Time Machine snapshots
Clear browser caches
Delete old iOS backups (~/Library/Application Support/MobileSync/Backup/)

Documents:

Use “Optimize Storage” (moves old files to iCloud)
Empty Trash
Review large files

Applications:

Uninstall unused apps

Limitations:

Recommendations are generic (not personalized to your actual usage)
Doesn’t identify specific large files
Requires manual navigation to delete files

Built-in Method 2: Spotlight Search for Large Files

Spotlight can find large files, but it’s slow and clunky.

How to Find Files > 1 GB:

Open Spotlight (Cmd + Space)
Type: kind:document size:>1GB
Browse results

Other search patterns:

kind:movie size:>500MB
kind:image size:>100MB
kind:pdf size:>50MB

Limitations:

No visual representation — Just a list of files
Slow for large drives — Spotlight takes time to index
No folder-level analysis — Can’t see “this folder has 50 GB total”
Tedious manual searching — Have to repeat searches for different sizes/types

Lesson: Spotlight finds individual files, but doesn’t give you the big picture.

Built-in Method 3: Terminal Commands (Advanced)

For developers comfortable with Terminal, you can find large files manually:

Find Largest Files in Home Directory:

du -h ~ | sort -rh | head -n 20

What this does:

du -h ~ — Disk usage of home directory (~), human-readable
sort -rh — Sort by size, largest first
head -n 20 — Show top 20 results

Output example:

147G  /Users/yourname
 52G  /Users/yourname/Library
 25G  /Users/yourname/Library/Developer/Xcode/DerivedData
 18G  /Users/yourname/Downloads
 12G  /Users/yourname/Library/Caches

Find Largest Files (Not Folders):

find ~ -type f -size +1G -exec ls -lh {} \; | awk '{print $5, $9}'

What this does:

find ~ -type f -size +1G — Find files (not folders) larger than 1 GB
ls -lh — List in human-readable format
awk '{print $5, $9}' — Extract size and file path

Limitations:

Not user-friendly — Requires Terminal knowledge
No visual representation — Just text output
Slow for large drives — Can take minutes to complete
Doesn’t show folder hierarchy — Hard to understand context

When to use: Quick one-off check for a specific folder.

Built-in Method 4: Finder “Calculate All Sizes”

Finder can show folder sizes, but you have to enable it:

How to See Folder Sizes in Finder:

Open Finder
Press Cmd + J (Show View Options)
Check “Calculate all sizes”

What you’ll see:

File/folder sizes displayed in list view

Limitations:

Extremely slow — Finder calculates sizes one by one
No sorting by size — Can’t easily see largest folders first
No treemap visualization — Still hard to spot space hogs

Lesson: Finder wasn’t designed for storage analysis.

The Problem with Built-in Tools

All built-in methods have the same core issues:

No visual hierarchy — Can’t see the “tree” of where space is used
Slow analysis — Takes minutes to scan large drives
No actionable insights — Doesn’t suggest what to delete
Manual cleanup — Have to delete files one by one in Finder

What you actually need:

Visual treemap — See proportional space usage at a glance
Fast scanning — Analyze 500 GB in seconds, not minutes
Drill-down navigation — Click folders to see what’s inside
Quick actions — Delete or reveal files directly from the analyzer

This is what disk space analyzers solve.

The Better Solution: Visual Disk Analyzers

Third-party disk analyzers scan your drive and show space usage as an interactive treemap. Here’s an honest comparison:

1. Storage Peek (This is mine)

What it does:

Scans entire drive in ~10 seconds
Visual treemap (bigger rectangles = more space)
Click rectangles to drill down into folders
Right-click to reveal in Finder or move to Trash
Color-coded by file type
Menu bar widget for at-a-glance storage stats

Why it’s fast:

Multi-threaded scanning (uses all CPU cores)
Optimized for SSDs (parallel directory traversal)
Caches results (re-scan only changed folders)

Pricing: Free

Best for: Quick visual analysis without learning Terminal commands. See exactly what’s using space in seconds.

Download Storage Peek →

2. DaisyDisk

What it does:

Beautiful sunburst visualization (circular treemap)
Smooth animations and polished UI
Scan results saved for comparison over time
Admin mode to scan system files

Why it’s popular:

Gorgeous design (Apple Design Award winner)
Intuitive interaction model
Reliable and actively maintained

Pricing: $9.99 (one-time purchase)

Best for: Users who want the most polished experience and don’t mind paying $10.

3. Disk Inventory X (Free)

What it does:

Classic treemap visualization
Fast scanning
Detailed file info panel

Limitations:

Not updated since 2013 (still works on modern macOS)
Outdated UI — Feels like software from 2010
No modern macOS features (no Dark Mode, no menu bar widget)

Pricing: Free (open source)

Best for: Users who want a free tool and don’t care about modern design.

4. OmniDiskSweeper (Free)

What it does:

Simple list-based view (sorted by size)
Shows folder hierarchy
Quick reveal/delete actions

Limitations:

No treemap visualization — Just a list
Slower than modern analyzers — Single-threaded scanning
Basic UI — Functional but not intuitive

Pricing: Free

Best for: Users who prefer list view over treemaps.

5. GrandPerspective (Free, Open Source)

What it does:

Treemap visualization
Multiple color schemes
Filter by file type/size

Limitations:

Slow scanning — Not optimized for modern SSDs
Clunky navigation — Harder to drill down than DaisyDisk or Storage Peek

Pricing: Free (open source)

Best for: Open-source enthusiasts who want a free treemap tool.

My Recommendation (Honest Comparison)

Tool	Best For	Pros	Cons	Price
Storage Peek	Fast, affordable visual analysis	Fastest scanning, modern UI, menu bar widget	Fewer features than DaisyDisk	$2.99
DaisyDisk	Polished UX, willing to pay	Beautiful design, smooth animations	$9.99 cost	$9.99
Disk Inventory X	Free + don’t care about design	Free, fast enough	Outdated UI, no updates since 2013	Free
OmniDiskSweeper	Prefer list view	Simple, reliable	No treemap, slower	Free
GrandPerspective	Open-source advocates	Free, customizable	Slow, clunky	Free

If I had to pick one:

Free: Storage Peek (fast + modern) or Disk Inventory X (tried and true)
Paid: DaisyDisk if you value design and smooth animations

Avoid: Buying “Mac cleaner” apps (CleanMyMac, CCleaner) — they’re expensive ($30-90/year) and overpromise. A simple disk analyzer is all you need.

How to Actually Clean Up Space

Once you’ve found what’s using space, here’s how to clean it up safely:

1. Developer Files (20-100 GB)

Xcode Derived Data:

rm -rf ~/Library/Developer/Xcode/DerivedData

Xcode regenerates this automatically. Safe to delete.

npm/yarn cache:

npm cache clean --force
yarn cache clean

Homebrew cache:

brew cleanup

Docker images:

docker system prune -a

CocoaPods cache:

pod cache clean --all

2. Browser Caches (5-20 GB)

Safari:

Safari → Preferences → Advanced → Check “Show Develop menu”
Develop → Empty Caches

Chrome:

Settings → Privacy and security → Clear browsing data
Select “Cached images and files” → Clear data

Firefox:

Preferences → Privacy & Security → Cookies and Site Data → Clear Data

3. Application Caches (10-50 GB)

Spotify cache:

rm -rf ~/Library/Caches/com.spotify.client

Slack cache:

rm -rf ~/Library/Application\ Support/Slack/Cache
rm -rf ~/Library/Application\ Support/Slack/Service\ Worker/CacheStorage

VS Code extensions:

rm -rf ~/.vscode/extensions

(Reinstall extensions you actually use)

4. iOS Backups (10-100 GB)

Location:

~/Library/Application Support/MobileSync/Backup/

To delete:

Open Finder
Press Cmd + Shift + G
Paste path above
Delete old backups (keep most recent one)

Better solution: Use iCloud backups instead of local backups.

5. Time Machine Local Snapshots (10-50 GB)

Check snapshots:

tmutil listlocalsnapshots /

Delete old snapshots:

tmutil deletelocalsnapshots 2024-01-15-123456

(Replace with snapshot date from list)

Or let macOS manage automatically: Time Machine deletes old snapshots when disk space is low. Don’t manually delete unless desperate.

6. Downloads Folder (5-50 GB)

Common space wasters:

Old .dmg installers (delete after installing app)
.zip archives (extract and delete archive)
Large PDFs (move to Documents or cloud storage)

Quick cleanup:

Open Downloads folder
Sort by Size (Cmd + J → Arrange by Size)
Delete installers and archives

7. Duplicate Files (5-20 GB)

Use Gemini 2 (paid app) or Duplicate File Finder (free) to find duplicates.

Manual method:

fdupes -r ~/Documents

(Requires brew install fdupes)

8. Old Mail Attachments (5-30 GB)

Mail.app stores attachments locally:

~/Library/Mail/V10/MailData/Attachments/

To clean up:

Open Mail
Mailbox → Erase Deleted Items
Preferences → Accounts → Select account → Advanced → Uncheck “Keep copies of messages for offline viewing” (IMAP accounts)

9. Photos Library (50-200 GB)

If using iCloud Photos:

Photos → Preferences → iCloud
Check “Optimize Mac Storage”
macOS keeps thumbnails locally, full-res in iCloud

If not using iCloud:

Move old photos to external drive
Use Photos → File → Export to save originals

10. Large Log Files (1-10 GB)

System logs:

sudo rm -rf /private/var/log/*

(macOS regenerates logs automatically)

Application logs:

rm -rf ~/Library/Logs/*

Safe to delete: Yes, logs are for debugging. Apps create new logs as needed.

What NOT to Delete

Dangerous paths to avoid:

/System/ — System files (breaks macOS)
/Applications/ (unless uninstalling known apps)
~/Library/Preferences/ — App settings
~/Library/Keychains/ — Saved passwords
~/Library/Application Support/ (unless you know what you’re deleting)

Rule of thumb: If you don’t recognize it, don’t delete it. Use a disk analyzer to identify safe targets (like caches and old downloads).

Preventing Future Storage Crises

1. Enable “Optimize Storage”

System Settings → General → Storage:

✅ Store in iCloud (moves old files to cloud)
✅ Optimize Storage (removes watched movies/TV)
✅ Empty Trash Automatically (deletes files after 30 days)
✅ Reduce Clutter (shows large/old files to review)

2. Use External Drives for Large Media

Move Photos/Music/Videos to external SSD
Keep only active projects on internal SSD

3. Clean Up Monthly

Set a calendar reminder to:

Empty Downloads folder
Clear browser caches
Delete old Xcode derived data (if developer)

4. Monitor Storage Continuously

Use a menu bar app (Storage Peek, DaisyDisk) to see storage usage at a glance. Catch problems before disk fills up.

FAQ

What is “System Data” and why is it so large?

System Data (formerly “Other”) includes:

macOS system files and caches
iOS device backups (~/Library/Application Support/MobileSync/Backup/)
Time Machine local snapshots
Spotlight index
App caches (browser, Slack, Spotify, etc.)

Normal size: 20-50 GB Bloated size: 100-200+ GB (indicates old backups or excessive caches)

To reduce:

Delete old iOS backups
Clear browser/app caches
Remove Time Machine snapshots
Reboot (clears some temporary caches)

Should I use “Clean My Mac” or similar apps?

Honest answer: Mostly unnecessary.

What they do:

Scan for caches/logs (you can do this manually)
Uninstall apps (Finder can do this)
Find large/duplicate files (free disk analyzers do this)

Cost: $30-90/year (subscription)

Better approach:

Use free disk analyzer (Storage Peek, Disk Inventory X)
Manually delete caches (see “How to Clean Up” section above)
Use AppCleaner (free) to fully uninstall apps

Exception: If you have zero technical knowledge and want one-click cleanup, CleanMyMac X is reputable (but overpriced).

Why does my Mac say storage is full but I just deleted files?

Cause 1: Trash not emptied

Files in Trash still count as used space
Finder → Empty Trash

Cause 2: Time Machine snapshots

macOS keeps local backups even after deleting files
Snapshots auto-delete when space is needed
Or manually delete: tmutil deletelocalsnapshots [date]

Cause 3: iOS backups

Old iPhone/iPad backups eating 50+ GB
Delete in Finder (see “iOS Backups” section above)

Cause 4: “Purgeable” space

macOS marks some files as “purgeable” (can be deleted if needed)
Storage Management shows this separately
macOS auto-purges when installing large apps

How do I find duplicate files on Mac?

Free tools:

Gemini 2 (free trial, then $19.95)
dupeGuru (free, open source)
fdupes (Terminal: brew install fdupes)

Manual method:

Use disk analyzer (Storage Peek, DaisyDisk)
Look for folders with many files of same size
Manually compare and delete

Common duplicate sources:

Downloads folder (same file downloaded twice)
Photos (imported from multiple sources)
Music (iTunes + local files)

Is it safe to delete ~/Library/Caches?

Yes, but…

Apps will recreate caches as needed
You’ll lose some app preferences (like recently opened files)
Some apps may launch slower first time (rebuilding cache)

Better approach:

Delete specific app caches (see “Application Caches” section)
Don’t blindly delete entire ~/Library/Caches folder

Nuclear option (if disk is critically full):

rm -rf ~/Library/Caches/*

Then reboot. Apps will regenerate caches.

Conclusion

“What’s taking up space on my Mac?” has a simple answer: large files in unexpected places.

Action plan:

Use a disk analyzer — Storage Peek ($3) or DaisyDisk ($10)
Identify space hogs — Developer files, caches, old backups, downloads
Clean up safely — Follow the “How to Clean Up” section above
Prevent future problems — Enable “Optimize Storage”, monitor monthly

Quick wins for developers:

Delete Xcode DerivedData (20-50 GB)
Clear npm/yarn cache (5-20 GB)
Remove old Docker images (10-50 GB)

Quick wins for everyone:

Empty Downloads folder (5-50 GB)
Delete old iOS backups (10-100 GB)
Clear browser caches (5-20 GB)

Related guides:

Mac Storage Management Guide
How to Clean Xcode Cache (coming soon)
Mac Storage ‘Other’ Explained (coming soon)

Want instant storage analysis? Try Storage Peek →