WhySlow
What is mdworker_shared on Mac?
Reads the contents of files so Spotlight can search them.
Why is mdworker_shared using so much CPU?
Busy when many new or changed files need indexing, like builds or big downloads.
Should you quit mdworker_shared?
No. mdworker_shared 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 mdworker_shared a virus?
No. mdworker_shared 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 mdworker_shared 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 mdworker_shared on your Mac
Open Activity Monitor (Applications › Utilities), choose the CPU tab and type mdworker_shared 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 mdworker_shared in plain English and only flags it when it is really slowing your Mac down.
What to do if mdworker_shared 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 mdworker_shared 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 mdworker_shared
- Shows how much CPU and memory mdworker_shared 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 mdworker_shared is the real cause of a slow Mac, and when it isn't.
Free to explain. $7 once for one-click fixes.