WhySlow
What is mds on Mac?
Runs Spotlight search and decides what to index.
Why is mds using so much CPU?
Busy after a macOS update, a large file copy, or plugging in a drive.
Should you quit mds?
No. mds is part of macOS. Quitting it can break things, and macOS starts it again anyway. When it is busy, it usually settles on its own.
Is mds a virus?
No. mds is a genuine part of macOS, signed by Apple and stored in a protected system folder that apps can't change. Malware sometimes borrows familiar names, so if a process called mds lives outside /System or /usr, or you see it after installing something unusual, run a check with a trusted tool and keep macOS up to date.
How to check mds on your Mac
Open Activity Monitor (Applications › Utilities), choose the CPU tab and type mds in the search field. The % CPU column shows how busy it is: 100% means one full processor core. The Memory tab shows how much memory it uses. Activity Monitor shows numbers but doesn't say what they mean; WhySlow explains mds in plain English and only flags it when it is really slowing your Mac down.
What to do if mds stays busy
- Give it time. After a macOS update or a big file copy, Spotlight can index for a few hours. Keep the Mac plugged in and awake.
- Keep busy folders out of the index: open System Settings › Spotlight › Search Privacy and add folders like Xcode DerivedData, Docker data or virtual machine folders.
- If mds has been busy for more than three hours, the index is probably stuck. Rebuilding it usually fixes this: WhySlow does it in one click, or run “sudo mdutil -E /” in Terminal.
How WhySlow helps with mds
- Shows how much CPU and memory mds is using right now, in plain English.
- Opens Spotlight settings so you can keep big folders out of the index.
- Rebuilds the Spotlight index when indexing has been stuck for hours (one-click fix).
- Tells you when mds is the real cause of a slow Mac, and when it isn't.
Free to explain. $7 once for one-click fixes.