Mac Storage Manager: How to Check and Free Space

Why It's Worth Checking Your Storage First

When your Mac warns that the startup disk is almost full, the temptation is to start deleting things at random. That's a mistake. Storage on macOS is not evenly distributed — a handful of large files, caches, or forgotten backups usually account for the bulk of the problem. If you check first, you can reclaim 20 or 30 GB by removing a few items instead of painstakingly trimming your Documents folder for hours.

macOS gives you two built-in tools for this, and there's a third file-level approach for when you need real detail. We'll walk through all three, from quickest to most thorough.

Method 1: The Built-In Storage Overview

This is the fastest way to see a categorised breakdown of what's on your drive. On macOS Ventura, Sonoma, and later:

1. Open the Apple menu in the top-left corner of the screen and choose System Settings.
2. Click General in the sidebar, then click Storage.
3. Wait for the bar to calculate. A coloured bar appears at the top showing categories like Applications, Documents, macOS, and System Data.
4. Hover over each segment to see its exact size, and scroll down to the list of recommendations and per-category detail rows.

On macOS Monterey and earlier, the path is different: open the Apple menu, choose About This Mac, click the Storage tab, then click Manage to open the storage management window. The categories and cleanup tools are the same.

Method 2: Disk Utility (Free Space and Volumes)

Disk Utility is the right tool when you care about the raw disk picture — total capacity, free space, and how your APFS volumes and containers are laid out. It's especially useful if you have multiple partitions or a Boot Camp/Windows volume.

1. Open Disk Utility. Press Command + Space, type "Disk Utility", and press Return. Or find it in Applications > Utilities.
2. Select your drive. In the sidebar, click your internal disk (often named "Macintosh HD") or its container.
3. Read the capacity bar. The panel shows total capacity, used space, and available space, colour-coded by what's occupying the volume.
4. Check View > Show All Devices if you want to see the physical disk, its APFS container, and every volume that shares free space within it.

Disk Utility won't tell you which files are large, but it gives you the ground truth on free space that the storage overview sometimes rounds or reports optimistically (macOS counts "purgeable" space as available).

Method 3: A Full File-Level Breakdown

The two built-in tools tell you your storage is being used, but not by what, exactly. To find the specific folders and files eating your space, you need a storage analyzer that maps every file on disk and ranks it by size.

This is where a dedicated tool earns its keep. TrimyMac's Storage Analyzer scans your entire drive, builds a visual, drillable map of your folders, and lets you sort by size so the biggest offenders float to the top instantly. Instead of guessing, you see that a single old iOS backup is 18 GB, or that a forgotten Downloads archive is 9 GB — and you can act on it in the same window.

You can also do a rough version in Finder: open your home folder, switch to List view (Command + 2), enable the Size column, and sort by it. But Finder does not calculate folder sizes by default and can be slow to do so, which is why a purpose-built analyzer is far more practical for a whole-disk view.

Understanding the Storage Categories

The coloured bar in the storage overview uses categories that aren't always self-explanatory:

• Applications — everything in your /Applications folder.
• Documents — user files across your home folder, including large files in Downloads and Desktop.
• System Data — the modern catch-all (formerly "Other"): caches, logs, snapshots, and files macOS can't categorise. This is often the most confusing and the most reclaimable.
• macOS — the operating system itself, typically 12–20 GB. You cannot and should not reduce this.
• Photos, Music, Mail, Messages — content from Apple's built-in apps.

What Is "Purgeable" Space?

You may notice your Mac reports more free space than you can account for. That's "purgeable" space — files macOS considers safe to delete automatically when the disk fills up, such as cached iCloud files that also live in the cloud, and old local snapshots. macOS optimistically counts this as available. It's real, but it's not instantly usable, which is why Disk Utility's free-space number can differ from the storage overview. If you need space right now, cleaning caches and large files gives you space you can rely on immediately.