How to Free Up Storage Space on Mac Before a macOS Update
macOS updates can fail or stall when your disk is nearly full. This guide shows you how to quickly reclaim gigabytes of space — using built-in tools, clearing System Data and caches, finding large files, and offloading to iCloud — so your macOS Tahoe update installs cleanly.
Table of Contents
How Much Space Does a macOS Update Need?
A macOS point update (like macOS Tahoe 26.5) typically needs 15–25 GB free to download and install, even though the download itself is only a few gigabytes — macOS needs working room to unpack and apply the update. A major upgrade (a new version like macOS Tahoe 26) can need 25–45 GB free.
Rule of Thumb
Aim to keep at least 20 GB free at all times, and 40 GB+ before a major upgrade. Macs that run consistently full also suffer slower performance because macOS can't manage swap and caches efficiently.
Check Your Current Storage
Open Storage Settings
- Go to System Settings → General → Storage.
- Wait a moment for the colored bar to calculate.
- Hover over each segment (Apps, Documents, System Data, etc.) to see how much each is using.
This screen is also where Apple's storage recommendations live.
Use the Built-In Storage Tools
macOS includes four one-click recommendations in Storage. They're the safest first step:
Store in iCloud
Moves files, photos, and messages to iCloud, keeping only recent items on-device. Frees the most space but requires enough iCloud storage.
Optimize Storage
Automatically removes watched Apple TV movies and shows, and old email attachments, when space runs low.
Empty Trash Automatically
Permanently deletes items that have been in the Trash for more than 30 days.
Review Files (Documents)
Opens a browser of large files, downloads, and unsupported apps so you can delete them individually.
Find and Delete Large Files
Use the Documents Recommendation
In Storage, click Documents. Use the Large Files, Downloads, and File Browser tabs to spot space hogs. Sort by size and delete what you don't need.
Clear the Downloads Folder
The Downloads folder is a classic hiding place for old installers (.dmg, .pkg), zip files, and duplicates. Open it in Finder, switch to list view, sort by size, and clear out the big stuff.
Remove Unused Apps
Open the Applications tab in Storage, sort by size, and uninstall apps you no longer use. Large creative and virtualization apps can reclaim several gigabytes each.
Tame "System Data"
"System Data" (formerly "Other") is the catch-all category that can balloon to tens of gigabytes. It includes caches, logs, temporary files, and old update files.
Clear User Caches Safely
Caches usually clear themselves, but you can prompt macOS to rebuild them:
- In Finder, choose Go → Go to Folder and enter
~/Library/Caches. - Move the contents to the Trash (leave the folder itself).
- Restart your Mac so caches rebuild cleanly.
Caution
Only clear caches inside ~/Library (your user library). Avoid deleting from the system-level /Library or /System unless you know exactly what a file does.
Thin Out Time Machine Local Snapshots
macOS keeps local Time Machine snapshots that count toward System Data. They're usually purgeable automatically, but a restart and a fresh backup help macOS release the space. Most of System Data is reclaimed by macOS on demand when the disk fills.
Empty Trash & Clear Purgeable Space
- Right-click the Trash in the Dock and choose Empty Trash.
- Empty the in-app trash in Photos (Recently Deleted) and Mail.
- Restart your Mac — this prompts macOS to release "purgeable" space that the Storage bar may still show as used.
Tip
If the update still says there isn't enough space even though Storage looks fine, it's often purgeable space that hasn't been released yet. A restart, or simply starting the update (macOS frees purgeable space as needed), usually resolves it.
Offload to iCloud & External Drives
For long-term breathing room:
- Move large photo and video libraries to an external SSD.
- Enable iCloud Photos with "Optimize Mac Storage" so full-resolution originals live in the cloud.
- Archive completed projects to external or cloud storage rather than keeping them on the startup disk.
Frequently Asked Questions
macOS needs temporary working space to unpack and install an update — often 2–3× the download size. Free up to the recommended 15–25 GB and restart before retrying.
Usually not. The built-in Storage tools plus emptying Trash and Downloads handle most situations. Be cautious with aggressive "cleaner" apps that delete system files — they can cause more problems than they solve.
You can't delete it directly, and you shouldn't try to force it. Clear your user caches, empty trash, remove old downloads, and restart — macOS reclaims most System Data automatically.
Conclusion
Freeing space before a macOS update prevents the most common cause of failed and stuck installs. Start with the built-in Storage recommendations, clear Downloads and user caches, empty the Trash, and restart. With 20 GB+ free, your macOS update should install smoothly. If it still gets stuck, see our guide on fixing a stuck "Preparing Update."