How to Free Up Space on an iMac in 2026 (Fusion Drive & SSD)

If your iMac storage is full, the fix depends heavily on which iMac you have. Late-2012 through 2019 iMacs shipped with Fusion Drive — a hybrid of a small SSD and a spinning hard disk — and that architecture creates storage problems that general Mac cleanup advice completely ignores. This guide covers how to free up space on an iMac regardless of model, with a dedicated section on Fusion Drive quirks that rarely get addressed.

Understanding Your iMac's Storage Type

Before cleaning anything, confirm what you are working with.

1. Click the Apple menu → About This Mac → More Info (macOS 13+) or System Report.
2. Select Storage in the sidebar.
3. If you see two entries — typically a 24 GB or 128 GB SSD alongside a 1 TB or 2 TB HDD — your machine uses a Fusion Drive managed by Core Storage.
4. A single entry labeled "Apple SSD" or "APPLE SSD" means you have a pure-flash iMac (2017 and later 27-inch, all 2021 M1 models, and all M3/M4 models).

Why Fusion Drive iMacs Fill Up Differently

The Fusion Drive presents itself to macOS as a single logical volume, but underneath, macOS (via Core Storage or APFS Fusion on macOS 10.14+) promotes frequently accessed blocks to the SSD tier and demotes cold data to the HDD. When the HDD portion is nearly full, the promotion engine stalls, the whole logical volume appears full, and performance tanks — spinning-disk seeks now dominate even for "hot" files.

The practical consequence: you may see iMac storage full warnings when only the HDD partition is full, even if the SSD tier has free room. macOS cannot automatically balance across the tiers when the HDD side is exhausted.

Clearing space on a Fusion Drive therefore means actually reducing the data on the logical volume — not just reorganizing which tier holds what. The SSD tier will re-balance itself once overall free space improves.

Step 1 — Check What Is Eating Your Space

1. Open System Settings → General → Storage. The colored bar shows broad categories but often lumps GB into an opaque "System Data" bucket.
2. For a more precise picture, open Terminal and run:

   du -sh ~/Library/Caches/*  | sort -rh | head -20

   This lists your largest per-app cache folders.
3. To audit your entire home folder by top-level directory:

   du -sh ~/* | sort -rh

On a Fusion Drive iMac this step is especially important because large video project folders, VM images, or photo libraries on the HDD tier are often the root cause of an iMac Fusion Drive full situation — and no amount of cache clearing alone will solve it if you have a 80 GB Final Cut library sitting in ~/Movies.

Step 2 — Clear Caches and System Data (Safe Wins)

Caches are designed to be deleted; macOS will rebuild them on demand. However, cleaning is permanent, so close applications before removing their cache folders.

User caches

1. Quit all apps.
2. In Finder, press Shift-Command-G and go to ~/Library/Caches.
3. Sort by size. Safe to delete: per-app subfolders for apps you actively use (e.g. com.apple.Music, com.google.Chrome). The apps rebuild them at next launch.
4. Do not delete ~/Library/Caches/com.apple.HomeKit or any folder you cannot identify — use the 'Is this safe to delete?' feature in Crumb if you are unsure.

System-level caches and logs

# View size of system log directory (read-only; sudo required to delete)
sudo du -sh /private/var/log
sudo du -sh /private/var/folders

System caches under /private/var/folders are managed by macOS and are generally safe to clear via a proper tool, but manually deleting them with rm -rf is risky — file locks and permissions errors can leave partial states. A cleaner path is to use About This Mac → Storage → Manage and click Review Files under "System Data," or use a dedicated tool.

Download Crumb if you want a one-click approach: its Clean action targets System Data, user caches, logs, temp files, and purgeable space in a single pass — useful on Fusion Drive iMacs where every GB recovered from the HDD tier actually matters for drive longevity and tier-promotion headroom.

Step 3 — Remove App Leftovers

Dragging an app to the Trash leaves behind preference files, caches, Application Support folders, and sometimes gigabyte-scale model or plugin directories scattered across ~/Library. On older iMacs with limited Fusion Drive space this accumulates fast.

1. In Finder, press Shift-Command-G → ~/Library/Application Support and sort by size.
2. Look for folders named after apps you deleted months ago.
3. Before deleting, verify the parent app is actually gone: ls /Applications | grep -i "AppName"
4. If the app is gone, the leftover folder is safe to remove.

Crumb's Uninstall tab automates this: it scans for installed apps, lets you select one for removal, and surfaces all associated leftover files as a checklist before anything is deleted — so you confirm each item rather than blindly purging.

Step 4 — Deal With Large Files and Duplicates

• Find files over 1 GB: find ~ -size +1G -not -path "*/.*" 2>/dev/null
• Downloads folder: Sort by size in Finder (View → as List → Size). Old disk images (.dmg), zip archives, and installer packages are common culprits.
• iCloud off-load: In System Settings → Apple Account → iCloud → iCloud Drive, enable "Optimise Mac Storage" to keep remote-only copies of older files.
• Time Machine local snapshots: On Fusion Drive Macs, local snapshots can consume significant HDD space. Run tmutil listlocalsnapshots / to see them. macOS expires them automatically when space is needed, but you can delete specific ones: tmutil deletelocalsnapshots YYYY-MM-DD-HHMMSS

Step 5 — Fusion Drive-Specific: Check Core Storage Health

If your Fusion Drive iMac is running macOS Mojave or earlier (Core Storage, not APFS), you can inspect the logical volume group:

diskutil cs list

Look for "Logical Volume Group" and confirm its status is "Online." If you see errors or a degraded state, address that before any cleanup — a failing Fusion Drive needs a different solution (backup immediately, then consult Apple Support or consider replacing with a pure SSD).

On macOS Catalina and later, Fusion Drive uses APFS with a Fusion container. Check it with:

diskutil apfs list

A healthy Fusion container shows both the SSD and HDD physical stores contributing to the same container. Purgeable space reported here can be reclaimed by macOS automatically or accelerated by removing actual user data.

What Not to Do

• Do not run rm -rf /Library/Caches as root. System processes hold locks on some of these files; forcing deletion can leave macOS in an inconsistent state requiring a reinstall.
• Do not "split" a Fusion Drive to recover the SSD as a standalone unless you know exactly what you are doing. This erases all data on both drives.
• Do not trust "cleaner" apps that promise to remove "junk" without showing you exactly which files they intend to delete. Always review before confirming any deletion, because cleaning is permanent.

Summary: Prioritised Cleanup Order for iMac Storage

1. Identify the largest consumers with du or a disk visualiser.
2. Move or delete large user files (videos, old disk images, duplicate photos).
3. Clear user caches (~/Library/Caches) and review System Data via Storage settings.
4. Remove leftover files from deleted apps.
5. Enable iCloud optimised storage for off-loading older files.
6. On Fusion Drive Macs specifically: verify drive health with diskutil, and prioritise freeing at least 10–15% of total capacity to give the tiering engine room to operate.

Keeping a Fusion Drive iMac running well in 2026 is absolutely doable — it just requires a bit more deliberate housekeeping than a pure-SSD machine. Work through the steps above methodically, confirm each deletion before committing, and your iMac should regain both space and responsiveness.