Dupe guide

Stop getting the 'low disk space' warning on Mac

The low disk space warning is more than a nag — it can break things. Here's how to silence it permanently.

4 min read

The “Your startup disk is almost full” warning isn’t just annoying — when free space drops below about 5 GB, macOS starts misbehaving. Apps slow down or fail to save, Photoshop refuses to open, software updates fail. Here’s how to make the warning go away and stay away.

Why macOS needs free space

Modern macOS uses your disk as overflow RAM, for Time Machine snapshots, for app caches, for downloading updates. As a rule of thumb, keep 10–15% of your disk free. On a 512 GB drive, that’s about 50–80 GB of headroom.

If you’re below 5 GB free, things will break. The warning fires earlier (around 10–15% free).

Step 1: Get below the warning threshold

The fastest way to silence the warning today:

  1. Empty Downloads of DMGs and ZIPs.
  2. Delete old iOS backups (Finder > iPhone > Manage Backups).
  3. Turn on Photos > Settings > iCloud > Optimize Mac Storage.
  4. Empty Mail attachments cache (~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/).
  5. Empty the Trash.

That usually clears 5–30 GB on a typical Mac. Enough to silence the warning for now.

Step 2: Stop it coming back

The warning recurs because something is generating files faster than you clear them. Common drivers:

Step 3: Set up the auto-cleanup defaults

Two settings worth turning on:

  1. Finder > Settings > Advanced > "Remove items from the Trash after 30 days."
  2. System Settings > General > Storage > "Empty Trash Automatically."

Step 4: A monthly check

Calendar reminder. Once a month, open Terminal and run:

du -sh ~/* 2>/dev/null | sort -h | tail -5

That tells you your five biggest folders. If one has grown significantly, you know where to look.

When the warning is just inaccurate

Occasionally macOS reports inflated used space because of stale snapshot data or a Spotlight indexing bug. Try:

  1. Restart your Mac.
  2. Re-open About This Mac > Storage. Often it recalculates and you have several extra GB.

The duplicate angle

If the warning keeps coming back even after you clear caches and Downloads, duplicate files are usually why. Each new device sync, each saved-twice file, each “just in case” copy adds up.

Download Dupe for a one-time sweep. SHA-256 hashed duplicate detection, Trash-only (never permanent delete), skips system files. $14.99 one-time, no subscription. Run it once and the average Mac recovers 5–20 GB — usually enough to silence the warning for months.

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