Mac 'Your Startup Disk Is Almost Full' Warning

Overview

The macOS 'Your startup disk is almost full' warning means the system drive has very little free space, which can cause performance issues and crashes.

Key Details

• macOS needs at least 10-15 GB free for swap, caches, and updates
• Performance degrades significantly when disk is over 90% full
• macOS may fail to boot if the disk is completely full
• Virtual memory (swap) requires free disk space to function
• System updates require substantial free space (12-35 GB)

Common Causes

• Large files accumulated (videos, photos, downloads)
• Application caches and logs consuming space
• Time Machine local snapshots filling up the drive
• Xcode and iOS simulators consuming tens of GB
• Mail attachments and iMessage media stored locally

Steps

1. 1Check storage: Apple menu > About This Mac > Storage (or System Settings > General > Storage on Ventura+)
2. 2Empty Trash: right-click Trash icon > Empty Trash
3. 3Delete Time Machine local snapshots: tmutil listlocalsnapshots / then tmutil deletelocalsnapshots [date]
4. 4Clear application caches: ~/Library/Caches/ (delete contents, not the folder)
5. 5Use Finder > Go > Go to Folder > ~/Downloads and delete old downloads

Tags

More in Disk Errors

Frequently Asked Questions