Windows Search Indexer High CPU: Wait, Shrink or Rebuild

SearchIndexer.exe is the Windows Search service (WSearch) reading your files, email and other content so that Start, File Explorer and Outlook can find them instantly. High CPU or disk from it is normal for a while after Windows is installed or upgraded, after you add a large folder, or after the index is rebuilt. It becomes a problem when it never finishes, keeps starting over, or the index has grown far past what the indexer handles well. Read the indexing status first; most fixes are about making the index smaller, not about turning search off.

What the indexer is doing

Microsoft's indexing FAQ describes indexing as looking at files, email messages and other content and cataloging their information. The first run can take up to a couple of hours; after that it works in the background and only re-indexes data that changed.

How much work that is depends on how many items it indexes. Microsoft's search performance guide gives the scale:

The same guide notes that Outlook mailboxes on the PC are indexed by default, and a mailbox with more than 6 million items can degrade the indexer's performance.

Read the status before changing anything

In Windows 11, go to Settings › Privacy & security › Searching Windows and look at Indexed, which is the number of items. In Windows 10 it is Settings › Search › Searching Windows, Indexed Items. Newer Windows 11 builds call the page Search, with the indexing options under Find my files.

The status message tells you what kind of activity you are looking at:

Microsoft adds a warning to the maintenance case: problems writing the index often come before a drive failure, so make sure your personal data is backed up if that message keeps returning. Checking disk activity helps tell indexing load from a drive that is struggling.

Initial indexing or a loop

An initial index, or a rebuild, looks alarming but has an end. Microsoft says a rebuild can take up to 24 hours. During that time the Indexed number climbs, the status reads Indexing in progress, and the indexer backs off when you are typing or when the CPU or disk is busy with foreground work.

A loop looks different. Over several days the status never reaches Indexing complete, the Indexed number drops and climbs again, or the maintenance message keeps appearing. Note the item count once a day for two or three days before deciding which you have.

Choose Classic or Enhanced

The FAQ describes two scopes:

• Classic indexes your Documents, Pictures and Music folders plus the desktop by default, and balances search performance against resource use.
• Enhanced indexes your entire PC, including all user folders and files, and may use more system resources.

Enhanced on a PC with large project folders, photo libraries or game installs can push the item count into the range where Microsoft expects trouble. Switching to Classic and adding only the folders you search is often enough.

Exclude folders that do not need searching

Microsoft's guide shows two ways to shrink the index:

• Exclude whole folders: Settings › Privacy & security › Searching Windows › Add an excluded folder (Windows 10: Settings › Search › Searching Windows).
• Pick locations precisely: on the same page select Advanced indexing options (Windows 10: Advanced Search Indexer Settings), then in Indexing Options select Modify and tick or untick locations.

Good candidates are folders full of files you never search by name or content: build output and dependency folders in development projects, virtual machine disks, game libraries, large downloads you keep only as archives. Indexing Options › Advanced › File Types also lets you change how specific extensions are handled.

For Outlook, Microsoft suggests a shorter mail synchronization window than the default one year to reduce what is indexed.

Check how big the index really is

The index lives in C:\ProgramData\Microsoft\Search\Data\Applications\Windows, as Windows.db on Windows 11 and Windows.edb on Windows 10. Microsoft says to judge it by the Size on disk value in the file's Properties, not by the Size column in File Explorer, because the indexer's compression on sparse files makes the listed size inaccurate. A large database is a reason to narrow the scope, not to delete the file.

Troubleshooter and rebuild, in that order

Windows 10 includes a Search and Indexing troubleshooter. Microsoft lists it among the legacy troubleshooters being removed from newer Windows 11 releases, which point to Get Help under Settings › System › Troubleshoot › Other troubleshooters instead.

Rebuilding is the last step, and it is the right step after you change the scope so the index matches your new choices. In Windows 11: Settings › Privacy & security › Searching Windows › Advanced indexing options › Advanced › Rebuild. In Windows 10 the same button is under Advanced Search Indexer Settings › Advanced. Expect search results to be incomplete and the indexer to be busy for up to 24 hours, so start it in the evening with the PC plugged in.

What not to do

• Do not disable the Windows Search service to stop the CPU use. Search in Start, File Explorer and Outlook becomes slow or incomplete. Microsoft notes that some antivirus programs and "Optimize your PC" apps disable it, and recommends not running such apps if you want to use search.
• Do not rebuild repeatedly. Each rebuild starts the long initial run again; change the scope first, then rebuild once.
• Do not delete the contents of C:\ProgramData\Microsoft\Search\Data. Microsoft reserves that for the case where the settings page is greyed out and the service can no longer start.
• Do not end SearchIndexer.exe in Task Manager as a fix. It does not make the index any smaller, and the remaining work is still waiting the next time the service runs.

Mole for Windows stays out of the index itself. Its Optimize page has one task here, Start Windows Search, and it applies only when the service is set to start automatically but has stopped, which is what happens after a crash. A Windows Search service you turned off on purpose stays off. Mole does not rebuild, delete or resize the index, and on the Status page it does not offer End for the indexer, because it runs from the Windows folder.

For other background load, see high CPU usage on Windows and what Windows optimization does.

FAQ

Why is Windows Search Indexer using so much CPU?

Usually because it is building or updating the index: after installing or upgrading Windows, adding many files or rebuilding. Check Settings › Privacy & security › Searching Windows. If it says Indexing in progress, let it finish; if it never completes, reduce the scope.

How long does Windows indexing take?

Microsoft says the first index can take up to a couple of hours and a rebuild up to 24 hours. Very large indexes, above 400,000 items, take longer and are where performance problems start.

Is it safe to disable Windows Search indexing?

It does not harm Windows, but searching in Start, File Explorer and Outlook becomes slow or incomplete. Excluding folders or switching from Enhanced to Classic usually solves the CPU use while keeping search working.

Should I rebuild the search index?

Only after the status shows a problem that waiting does not fix, or after you change which folders are indexed. Each rebuild starts indexing from the beginning.