Why Is My Mac Running Out of Storage? A Complete Guide

Your Mac's storage didn't fill up overnight. It happened gradually — a cache file here, an old installer there, logs piling up in the background. One day you see the dreaded "Your disk is almost full" notification and wonder where all your space went.

Let's walk through the most common culprits and what you can do about each one.

The hidden ~/Library folder

Most of the space hogs on your Mac aren't in your Documents or Desktop folders. They're hiding in ~/Library, a folder that macOS keeps hidden by default. Inside it, you'll find:

• ~/Library/Caches — Every app you use stores temporary data here. Browsers alone can accumulate gigabytes of cached web content over time. Slack, Spotify, Discord, and other Electron apps are particularly aggressive with caching.

• ~/Library/Logs — Application logs grow continuously. Most are never read and serve no purpose after a few days. System logs, crash reports, and diagnostic data all pile up here.

• ~/Library/Application Support — This is where apps store their working data. Some apps, like chat clients or media tools, can store gigabytes of data here.

Old downloads you forgot about

Check your Downloads folder. Chances are you'll find .dmg files from apps you installed months ago, .pkg installers you ran once, and .zip archives you already extracted. These are pure dead weight.

Common offenders include: - .dmg disk images — These are installer containers. Once you've dragged the app to Applications, the .dmg serves no purpose. - .pkg files — System installers that run once and are never needed again. - .zip and .rar archives — If you've already extracted the contents, the archive is redundant.

Browser caches

Every browser maintains its own cache, and they can grow surprisingly large:

• Safari caches web content in ~/Library/Caches/com.apple.Safari/
• Chrome maintains caches in ~/Library/Caches/Google/Chrome/ plus Service Worker caches
• Firefox stores cache data in ~/Library/Caches/Firefox/
• Brave, Edge, and Arc each have their own cache directories

If you use multiple browsers, you might have several gigabytes of cached web data across all of them.

Xcode and developer data

If you've ever used Xcode, this is likely your biggest storage consumer. Xcode's DerivedData folder (~/Library/Developer/Xcode/DerivedData/) stores build artifacts for every project you've ever opened. It can easily reach 10-50 GB on an active developer's machine.

Other Xcode space consumers include: - iOS DeviceSupport — Debug symbols for every iOS version you've connected - Archives — Old app builds sitting in ~/Library/Developer/Xcode/Archives/ - Simulator data — Virtual device data for testing

System caches and logs

macOS itself generates cache and log data: - Spotlight indexes - Time Machine local snapshots - APFS snapshots - System diagnostic reports

What's actually safe to delete?

This is the crucial question. Not everything in ~/Library is safe to remove. Here's a general rule:

Safe to delete: Caches (they regenerate), old logs, completed downloads, Xcode DerivedData, browser caches.

Never delete: Keychains, Mail data, Photos libraries, iCloud data, Application Containers, SSH keys, or anything in ~/Library/Preferences.

A systematic approach

Rather than manually navigating hidden folders and guessing what's safe, a systematic scan gives you a clear picture. CleanMyMacOS scans 11 categories — user caches, logs, downloads, browser data, Xcode data, app leftovers, and more — and presents everything grouped by risk level. You review each item before anything is removed, and everything goes to Trash first so you can undo if needed.

The key is being informed before you delete. Knowing that a 3 GB cache folder belongs to an app you haven't used in months is different from blindly deleting cache folders and hoping nothing breaks.

CleanMyMacOS can help with this — download it free from the Mac App Store.