Spotlight Indexing High CPU on Mac: mds_stores Explained

Written for macOS 27 Golden Gate and macOS 26 Tahoe.

You update your Mac, open Activity Monitor because things feel warm and busy, and see processes you've never heard of at the top: mds, mds_stores, mdworker_shared. They can take a large share of the CPU for hours. That's Spotlight building its search index. Most of the time it's normal and it ends on its own. This guide shows how to tell normal indexing from a stuck loop, and how to calm it down without breaking search.

#Key takeaways

• mds, mds_stores and mdworker are Spotlight. They read your files so search can find them.
• Indexing after an update is expected. Apple says it can take hours or even days, depending on how much data you have.
• Help it finish. Keep the Mac idle, plugged in and online for a while, then restart.
• Exclude what you don't search, such as big build or VM folders, in Spotlight's Search Privacy list.
• Rebuild the index only if it's stuck, and use Apple's method first.

#What are mds, mds_stores and mdworker?

They are the processes behind Spotlight, and you'll see them in Activity Monitor whenever indexing is running.

• mds is the metadata server. Its manual page says it "serves all clients of the metadata APIs, including Spotlight."
• mdworker (and mdworker_shared) are worker processes. According to the manual page, mds uses them "to scan and index files as a volume is mounted or a file changes." You'll often see several at once.
• mds_stores manages the index databases themselves. When it's busy, Spotlight is writing a lot of new index data.

Their manual pages say the same thing for both: there's nothing to configure, and you shouldn't run them by hand. macOS starts and stops them as needed.

#Why does Spotlight use so much CPU after a macOS 27 update?

Apple's Spotlight article lists the moments when Spotlight indexes: when you first set up a device, after you install a software update or upgrade, and whenever data changes, such as when you install apps or receive new email. A major upgrade like macOS 27 Golden Gate touches a lot of the system at once, so Spotlight has a lot of re-reading to do.

Several other things make it take longer:

• How much data you have. Apple says indexing "can take hours or even days" depending on how much is on your device. A Mac with years of mail, photos and project folders takes longer.
• Folders that never stop changing. Code build output, virtual machine images, sync folders and downloads in progress all change constantly, and each change gives Spotlight more work.
• New volumes. Connecting an external drive or mounting a large disk image starts indexing for that volume too.
• Low disk space. The mdutil manual page notes that indexing "may be delayed due to low disk space or other conditions." On a nearly full disk, indexing can drag on.

Apple also lists Spotlight indexing as one of the intensive tasks that make the fans spin faster. If heat and noise are your main concern, see MacBook fan loud or running hot?

#How long should Spotlight indexing take?

Apple doesn't give a fixed number, only "hours or even days" for the initial indexing, with later updates "much faster." Here's a reasonable way to read it:

#How do I check if Spotlight is still indexing?

1. Open Spotlight. Press Command-Space. Apple says that on a Mac you'll see an indexing progress indicator at the top of the Spotlight window while indexing is underway.
2. Open Activity Monitor (Applications › Utilities), click CPU, and sort by % CPU. Look for mds, mds_stores, mdworker or mdworker_shared near the top.
3. Check the status in Terminal, if you prefer. This command is read-only and shows whether indexing is turned on for your startup disk:

# Shows Spotlight indexing status for the startup disk (read-only)
mdutil -s /

On a healthy Mac it prints Indexing enabled. It doesn't show progress, so pair it with a CPU snapshot:

# Top 10 processes by CPU; the second sample has the real numbers (read-only)
top -l 2 -o cpu -n 10 -stats pid,command,cpu | tail -11

We ask for two samples because the first one from top shows no CPU use. When we ran this on a Mac running macOS 26 Tahoe, mds_stores was in the top five, along with mediaanalysisd, which is Photos analysis rather than Spotlight.

#How do I calm Spotlight down without breaking search?

Start at the top. If things settle after a step, you can stop there.

1. Give it the conditions it needs. Apple says indexing finishes faster when the device isn't in use, is connected to power, and is online (some mail and other data may need to download). Leave the Mac plugged in, awake and on Wi-Fi or Ethernet for a few hours, or overnight.
2. Restart once. That clears any worker that has hung, and indexing picks up where it left off.
3. Install the latest update. Apple's first step for Spotlight problems is to install software updates. Check System Settings › General › Software Update. macOS 27.0.1 shipped on September 28, 2026.
4. Exclude folders you never search. Open System Settings, click Spotlight in the sidebar, then click Search Privacy in the lower right. Click the Add button, or drag folders in. Good candidates are build output, VM images, large archives and external drives you only use for storage.
5. Rebuild the index if it's stuck. Apple's method: in the same Search Privacy list, add the disk or folder you want to reindex, wait a few seconds, select it, click the Remove button, then click Done. Spotlight reindexes that location. Expect another round of high CPU while it does.

#Two cautions before you exclude anything

Apple notes two side effects in its guide:

• If you exclude a Time Machine backup disk, you'll keep seeing messages that Spotlight is indexing it. That indexing is required for Time Machine and can't be turned off.
• If you exclude certain files and folders, you might not be told about updates for some apps. Excluding the entire internal disk means you won't get update notifications at all.

#The Terminal rebuild, as a last resort

If Apple's method doesn't help, mdutil can erase and rebuild the index for a volume. This throws away the whole index for that volume. Search will be incomplete and CPU use high until it's rebuilt, which can take hours. It needs an administrator password.

# WARNING: erases and rebuilds the Spotlight index for the startup disk.
# Search is incomplete until indexing finishes. Use only if Apple's method failed.
sudo mdutil -E /

We haven't run this command on our test Mac for this guide, because it isn't read-only. Its syntax comes from the mdutil manual page on macOS 26.

#What not to do

• Don't keep force-quitting mds or mdworker. They're system processes. macOS starts them again, and the work starts over.
• Don't delete hidden index folders by hand, such as .Spotlight-V100 at the root of a volume. Use the Search Privacy list or mdutil instead.
• Don't exclude your whole internal disk to stop the CPU use. You lose search, and Apple says you also lose app update notifications.
• Don't rebuild the index on day one. Rebuilding while the first post-update indexing is still running just starts it again.
• Don't run indexing on battery in a bag. Busy CPU plus no airflow means a hot Mac. Let it work on a desk, plugged in.

#Watching CPU without opening Activity Monitor

Once you know that mds_stores is the cause, it helps to watch it settle without keeping Activity Monitor open. A small menu bar monitor with live CPU and a list of the busiest processes does that. Choose one that's lightweight, so it doesn't add to the load.

Freshist has a menu bar HUD with live CPU, GPU and memory readings, and its Status view lists the processes using the most CPU, power and memory. Its fan presets include Auto, which leaves the fans to macOS, and fan control goes back to macOS when you quit the app or remove its helper. If you want to cool things down while indexing runs, read is manual fan control safe on a Mac? first. There's more in the help docs, on how it compares and under pricing.

#Related guides

• Mac slow after the macOS 27 update? What's normal
• MacBook fan loud or running hot? What's normal
• Lost storage after the macOS 27 update? Here's why
• Developer caches on Mac: build folders are a common reason indexing never settles.
• Login items and background apps on Mac

#Sources

• Apple Support: About Spotlight indexing and search results on Apple devices
• Apple Mac User Guide: Prevent Spotlight searches in specific folders or disks on Mac
• Apple Support: About fans and fan noise in your Apple product
• Apple Activity Monitor User Guide: View CPU activity in Activity Monitor on Mac
• macOS manual pages: man mds, man mdworker, man mdutil (checked on macOS 26 Tahoe)
• MacRumors: Apple releases macOS Golden Gate 27.0.1 with bug fixes