mds_stores and mdworker

Indexing takes CPU and disk activity in proportion to how much needs indexing. A fresh index of a full disk can take a while. Folders that change constantly, such as build output, large caches or virtual machine images, can keep Spotlight busy for as long as they keep changing.

Several mdworker processes at once is normal. Spotlight runs more than one to scan files in parallel.

Open System Settings, go to Spotlight (Siri & Spotlight on some versions), click Search Privacy, and add the disk or folder. Spotlight stops indexing it and stops showing it in search results.

Good candidates are folders you never search and that change often, like build directories, package caches, or a folder of virtual machines.

If indexing never seems to finish or search results are wrong, Apple suggests rebuilding the index: add the disk or folder to the Search Privacy list, wait a few seconds, then remove it. Spotlight reindexes that location, which will keep mds_stores busy for a while.

Activity Monitor shows the processes, and Terminal can tell you whether indexing is turned on for a disk.

1. In Activity Monitor, click the CPU tab and type md in the search field. You will see mds, mds_stores, and one or more mdworker or mdworker_shared processes.
2. Watch their % CPU for a minute. Low or zero means Spotlight is idle. Steady activity means it is still working through files.
3. Click the Disk tab and look at the Bytes Read column for the same processes. Indexing reads a lot, so a count that keeps growing means scanning is still going on.
4. In Terminal, run mdutil -s / to see the indexing status of the startup disk. It prints Indexing enabled. when Spotlight is set to index that disk. For another disk, replace / with its path, such as /Volumes/Backup.

It depends on how many files need indexing, how fast the disk is, and how busy the Mac is with other work. A full index of a large disk takes much longer than catching up on a few changed files, and the same Mac can finish quickly one day and take hours after a big copy or a macOS update.

The better question is whether it is making progress. If mds_stores and mdworker get quieter over a few hours, it is finishing. If they stay busy day after day, something keeps changing files, or the index needs a rebuild.

If Spotlight stays busy long after an update or a migration, look for a location that keeps changing.

• Build output, node_modules, or package caches that are rewritten often.
• Virtual machine disk images or large databases that change while in use.
• A folder that another app writes to constantly, such as a download or sync folder.
• An external drive that is connected and disconnected often, which Spotlight checks each time it mounts.
• A damaged index, which is when rebuilding it from Search Privacy helps.

Do not turn Spotlight off for your whole startup disk to save CPU. Other features depend on the index, including searching in Finder, Mail and other apps. Exclude only the folders you do not need to search.

Quitting mdworker or mds_stores does not stop indexing, because macOS starts them again and they pick up where they left off. If you have Vitals' optional helper enabled, its 30 days of per process history make it easy to see whether indexing is winding down or coming back every day.