What is mdworker (mdworker_shared) on Mac?

mdworker, and mdworker_shared in recent versions of macOS, are Spotlight's helpers: they read the contents of your files so Spotlight can find them. They're safe. You may also see mdbulkimport.

Key points

• mdworker processes read new and changed files for Spotlight.
• They get busy with many new or changed files, often after an update or a big download.
• Many copies at once are normal; quitting them doesn't help for long.

What mdworker does

When a file is added or changed, macOS hands it to an mdworker, which reads its text, dates, authors and other details. mds_stores then adds what it found to Spotlight's index. Each mdworker handles one kind of file at a time, which is why there are often several.

Why is mdworker using so much CPU?

Many new or changed files, often after an update or a big download. Unpacking an archive, copying a folder of documents, or a build that writes thousands of files all give them work.

In one reading of a MacBook Pro (M1 Max, 64 GB) on October 10, 2026, mdworker was using 0.0% of the CPU and 10.4 MB of memory across 2 copies.

It settles on its own. More in Is Spotlight indexing slowing down your Mac?

Can I quit mdworker?

Stopping it doesn't help for long: macOS starts it again when it's needed.

How to check it

1. Open Activity Monitor: press Command-Space, type "Activity Monitor" and press Return.
2. Type mdworker in the search field at the top right.
3. Look at % CPU and Memory. Many copies of mdworker_shared are normal.

Questions

Is mdworker_shared a virus?

No. mdworker_shared is part of macOS: it's one of Spotlight's helpers that read your files.

Why are there so many mdworker_shared processes?

Each handles one kind of file at a time, so macOS runs several at once. They close when there's nothing left to read.

Why is mdworker using so much CPU?

Many files are new or changed, often after an update or a big download. It settles once Spotlight has caught up.