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greyspace · Guide

Why is my Spotlight index so big, and how do I rebuild it?

How to check the size of the Spotlight index on a Mac, why it can grow huge and land in System Data, and how to rebuild it safely from System Settings or with mdutil.

Where the index lives

Spotlight keeps its index for your startup disk in /System/Volumes/Data/.Spotlight-V100, a hidden folder that macOS protects. Storage settings counts it as System Data. On most Macs it's a modest share of the disk; when it goes wrong it can become one of the biggest things on it.

Check its size

Open Terminal (Applications › Utilities) and run this. It asks for your password, because the folder is protected, and prints one size.

sudo du -sh /System/Volumes/Data/.Spotlight-V100

While you're there, mdutil -s / tells you whether indexing is on. If the Mac feels busy and Activity Monitor shows mds_stores working hard, the index is being updated right now; give it time before you judge its size.

Why it gets so big

Rebuild it from System Settings

  1. Open System Settings › Spotlight and click Search Privacy… (on macOS 14 Sonoma: Siri & Spotlight › Spotlight Privacy…).
  2. Click + and add Macintosh HD (your startup disk). Confirm when macOS asks.
  3. Wait a minute, then select it in the list and click − to remove it. macOS throws the old index away and starts a new one.

Or rebuild it in Terminal

This erases the index of the startup disk and starts a fresh one. It's Apple's own tool and doesn't touch your files.

sudo mdutil -E /

What to expect afterwards

For a few hours, Spotlight and Mail search find less than usual and the Mac may run warmer while it re-indexes. Then search is back to normal, and the new index is usually much smaller than a broken one. Check the size again the next day.

Keep it small