What is mds_stores? Spotlight indexing on Mac explained

What mds, mds_stores, mdworker_shared and corespotlightd do

Spotlight is several processes working together. Apple documents two of them in macOS's manual pages and leaves the rest undocumented, so this is what the primary sources say, plus what we saw on macOS 27.0.1:

• mds is "the metadata server". It serves every app that searches file metadata, including Spotlight (man mds).
• mdworker_shared (older versions of macOS showed it as mdworker) is the worker that mds uses "to scan and index files as a volume is mounted or a file changes" (man mdworker). You'll often see several copies at once, each reading a file's contents and properties.
• mds_stores manages the index files themselves. Apple doesn't document it, but on macOS 27.0.1 it runs as a system user called _mds_stores, and that account's group is the one given access to each volume's hidden .Spotlight-V100 folder, where the index lives.
• corespotlightd is different. Apple's Core Spotlight framework lets apps add their own content to an index "so people can find it from Spotlight and Safari" (Apple Developer, Core Spotlight). Those entries are kept per app in ~/Library/Metadata/CoreSpotlight, separate from the file index (Eclectic Light, July 2026). corespotlightd runs in your own account and serves that app-supplied data.

The distinction matters for fixes: rebuilding the file index, below, does nothing for an app's own Core Spotlight data.

Why they're busy

Indexing work follows changes on disk. Expect mds_stores and mdworker_shared near the top of Activity Monitor:

• after a macOS update, which can change many files at once;
• after migrating to a new Mac or restoring from a backup, when the whole disk is new to Spotlight;
• when you connect an external drive for the first time, since each volume gets its own index;
• while you copy or download a lot of files;
• all the time, if a folder you own changes constantly: build folders for software projects, virtual machine disk images, or caches that sync clients rewrite.

The first four settle on their own. The last one is worth fixing, because the work never ends.

How long indexing should take, and how to check it

Apple gives no figure, and it depends on how many files you have and how fast the Mac is. A fresh index of a full disk can take hours; Eclectic Light reports that rebuilding every volume can take "many hours or days" (Eclectic Light). Leaving the Mac plugged in and awake helps it get through.

The reliable progress check is Activity Monitor: open the CPU tab and search for "md". When mds_stores and the mdworker_shared processes drop to almost nothing and stay there, indexing has caught up. Terminal's status command is read-only and tells you whether indexing is on, not how far it's got:

mdutil -s /

On a normal Mac it prints /: and then Indexing enabled. If it says indexing is disabled, Spotlight won't find new files until it's turned back on. mdutil -s -a lists every volume, including external drives.

Keep folders out of Spotlight

If a folder you never search changes all day, tell Spotlight to skip it. Open System Settings › Spotlight, click Search Privacy and add the folder. The button has the same name on macOS 15 Sequoia, macOS 26 Tahoe and macOS 27 (Apple, macOS 15; macOS 26). Good candidates are software build folders, virtual machine folders and external drives you only use for backups. Files in those places won't show up in Spotlight searches any more, which is the trade-off.

Spotlight not finding files? Rebuild the index

Rebuild the index only when it's broken: Spotlight misses files you know are there, or shows ones you've deleted. It isn't a speed fix, and while it runs your Mac works harder, not less.

The System Settings way

This is Apple's method (Apple, About Spotlight indexing and search results on Apple devices):

1. Open System Settings › Spotlight and click Search Privacy.
2. Drag your disk (usually Macintosh HD) or the folder you want reindexed into the list, or click the add button (+) and choose it. If you see a permissions error, your account doesn't own some items there; Apple's article links to how to fix that.
3. Wait a few seconds, then select the item in the list and click the remove button (–).
4. Click Done. Spotlight reindexes what you removed from the list.

The Terminal way

sudo mdutil -E /

-E erases the index stores for the volume, and the manual page says they "will be rebuilt if appropriate" (man mdutil). The index belongs to a system account (on macOS 27.0.1 the .Spotlight-V100 folder is owned by root), so the command uses sudo and asks for your administrator password. Nothing appears while you type it; press Return when you're done. If a single damaged file caused the problem, it can come back after a rebuild until that file is removed or excluded.

When it's something else

• Busy every day, not just after changes: look for the constantly changing folder above and exclude it.
• corespotlightd busy: most likely an app adding or updating its own search entries. That usually passes; if it doesn't, update or reinstall the app, since rebuilding the file index won't help.
• The Mac is slow and Spotlight isn't near the top: start with Why is my Mac so slow?
• Photo analysis after an update is a separate job with its own processes: see mediaanalysisd and photoanalysisd.

How Tend helps

Tend's free Energy & Apps page keeps 24 hours of per-app CPU and estimated watts, so you can see whether indexing is tailing off or still going strong, rather than guessing. If you do need a rebuild, Tend's Maintenance page (Pro) has Rebuild the Spotlight index, which runs the same mdutil -E / after you confirm and enter your administrator password, and suggests plugging in first if you're on battery.

Questions

Related guides

Sources

• Apple, About Spotlight indexing and search results on Apple devices (25 August 2026)
• Apple, Spotlight settings on Mac (macOS 15) and (macOS 26)
• Apple Developer, Core Spotlight
• macOS 27.0.1 manual pages: man mds, man mdworker, man mdutil
• Eclectic Light, When and how to rebuild Spotlight indexes (third party)
• Eclectic Light, Spotlight and Core Spotlight are different (third party)

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