mds_stores on Mac: what it is, why it is high, what to do

What mds_stores does

Spotlight is three processes working as a team. mds, the metadata server, decides what needs indexing and keeps the index consistent. mdworker (often several copies) opens each file and pulls out the text, dates, tags and other metadata. mds_stores takes what the workers found and writes it into the index files on each volume, in a hidden folder called .Spotlight-V100 at the root of the disk.

Howard Oakley describes the busy state exactly: when Spotlight is re-indexing, the processes taking CPU "should include mds_stores, mdworker (often multiple copies) and mds itself." If you see all three near the top of Activity Monitor, that is one job, not three problems.

Because mds_stores is the one doing the writing, it tends to show the highest sustained number of the three. It is also the one people search for, which is why it has a reputation it does not deserve. It is not a leak, not malware, and not something a cleaner app can fix. It is the index being built.

Why mds_stores is using CPU right now

1. A macOS update. Major versions change the index format and Spotlight rebuilds it. This is the single most common reason, and the one behind the Tahoe thread where a user found it "consistently using more than 85% of the CPU" with the fans running almost constantly. It finished; it just took longer than they expected.
2. A big import or download. Copying a photo archive, restoring from a backup, cloning a code repository with a hundred thousand files, downloading a game. Every new file gets indexed.
3. A drive it has not seen. Plug in an external SSD, a Time Machine disk, a camera card or a network volume and Spotlight starts indexing it. Time Machine volumes are a classic case: one Monterey user found Spotlight grinding through their backup drive and fixed both the CPU and failing backups by excluding that volume.
4. Apps that write constantly. Mail downloading a large account, a sync client like Dropbox or Google Drive hydrating files, a virtual machine or Docker writing to disk images. Each write is a re-index. The Apple Community replier VikingOSX summed it up: cloud sync clients, antivirus and cleaner apps "all will launch scores of indexing processes that will bog your Mac."
5. A damaged index. After a crash mid-write or a full disk, Spotlight can get stuck retrying the same files. Rarer than the forums suggest, and a restart often clears it.
6. A memory leak in a specific version. Reported occasionally; Michael Tsai's readers noted a case where "there seemed to be a memory leak within the mds_stores process." If memory climbs into many GB and never falls, update macOS.

What normal looks like, and what is not

How long a healthy index takes depends on how much changed. These are the typical shapes:

Two things that make the healthy case look worse than it is. First, Spotlight slows itself down when you are actively using the Mac and speeds up when you walk away, so a job that looks stalled at 30 percent while you work can finish in twenty minutes once you leave it. Second, on a laptop, indexing is paused or throttled on battery. If you keep closing the lid and unplugging, the same index can drag on for days of calendar time while only doing an hour of actual work.

The not-normal case is not the peak. It is the repeat: 85 percent again the next morning, or every time the same drive is plugged in, with the index never catching up.

Is it safe to quit mds_stores?

Quitting it in Activity Monitor is harmless: launchd restarts it within a second and it picks up the index where it left off. It is also useless for the same reason. You cannot "turn off" mds_stores without turning off Spotlight, and turning off Spotlight breaks search in Finder, Mail, the App Store and any app that relies on metadata, which is more than you would think.

So the answer is a soft no: do not bother. The safe way to reduce its work is to give it less to index, which is what the steps below do. If you want the general rule for any process, use the decision tree.

The one hard no: do not run Terminal commands from forum posts that delete the .Spotlight-V100 folder or use sudo mdutil to switch indexing off. Those posts tend to be the ones that end with search broken and the person reinstalling macOS.

What to do, in order

1. Plug in and walk away

   Connect power, leave the lid open, and give it an hour. Most mds_stores complaints are a normal re-index that the person kept interrupting. Check Activity Monitor afterwards; it is usually back under 5 percent.

2. See which volume it is indexing

   Open Spotlight (⌘Space) and type a word. While indexing is in progress, Spotlight shows "Indexing" with a progress bar and the drive name. That tells you whether it is your internal disk or something you plugged in.

3. Exclude the drive or folder that keeps triggering it

   System Settings, Spotlight (Siri & Spotlight on older versions), scroll to Search Privacy, click the plus button and add the Time Machine disk, the camera card, the virtual machine folder, the code checkout or whatever keeps feeding it. Spotlight stops indexing that location immediately. You lose search inside it, nothing else.

4. Pause the app that writes constantly

   If a sync client, mail account or download is pouring in files, pause it for an hour so the indexer can catch up. Then resume.

5. Restart

   A restart clears a daemon stuck on one bad file. If CPU comes back down and stays down, done.

6. Update macOS

   Point releases have fixed Spotlight bugs more than once, including leaks. System Settings, General, Software Update.

7. Rebuild the index, last resort

   In Search Privacy, add your startup disk (Macintosh HD), wait a minute, then select it and click the minus button. Spotlight deletes the index and rebuilds it from scratch. This takes an hour or more and search is incomplete until it finishes, so do it plugged in, overnight, and only after the steps above.

When to worry

mds_stores is one of the processes Oakley lists as a "regular offender" that is nevertheless normal. The cases where it is telling you something:

• Memory in the many GB and climbing. A leak in that macOS version. Update; restart in the meantime.
• Busy every time a specific drive is plugged in. That drive's index is damaged or the drive is failing. Exclude it; if the drive is also slow in Finder, back it up.
• Heat and battery. Hours of indexing on a laptop on your lap brings in kernel_task throttling and eats battery. Do the index on mains power.
• It never ends and nothing is feeding it. Rebuild the index. If even that does not help, something is writing to disk constantly; Safe to Quit tracks each process's disk writes over hours and shows which app kept the indexer busy, which Activity Monitor's snapshot cannot.

What is not a worry: the number itself. 100 percent for half an hour after an update is exactly what a working Mac does.