Rebuilding the Windows Search Index, which includes the Outlook Search, can resolve various issues:

• Windows Explorer does not responding but crashes or restarts.
• Whenever Windows Explorer is opened, it freezes and shows the "App Not Responding" dialogue. Then it crashes or shows the contents of the folder I clicked and freezes afterwards.
• Slow searching.
• Missing items in the index.
• Having trouble finding emails in Outlook?
• Is your search returning incomplete or incorrect results?
• If you search for items in Outlook and don't receive the results that you expect.

View the Index and it's Status

There are several ways and places to view the search index properties and its progress in rebuilding. After you have wiped your index it is useful to see how things are going.

• Indexing Options (Classic)
  
  
  • This will only show how many items are indexed and if there is indexing in progress. There are a few ways to view this window:
    1. Windows Key + I --> Privacy & security --> Search --> Find my files --> Classic --> Customise search locations
    2. Open Start menu and type: Indexing Options
    3. Outlook 2021 --> File --> Options --> Search --> Sources --> Indexing Options
• Windows Search (New)
  
  
  • Windows Key + I --> Privacy & security --> Search
  • Now look at the top of the page and you will see the number of Indexed items and Pending counter.
• Outlook Search Index
   
  • This will shows you how many items left to be indexed
  • Click in the search box
  • Toolbar --> Search Tab --> Search Tools --> Indexing status

Make Indexing faster

• Instructions from here: How to Enable or Disable Indexer Backoff in Windows | Windows 10 Forums

Disabling the indexer backoff will allow indexing to finish faster while you're active on the computer instead, but it will use more system resources.

• Run gpedit.msc
• Navigate to: Computer Configuration\Administrative Templates\Windows Components\Search: Disable indexer backoff:
• Set it to On (Default is Off)
• Restart the Windows Search service
• Once your index is rebuilt, set Disable indexer backoff  to Off and restart the Windows Search service.

Make Sure Outlook Emails are Indexed

• This only applies if you have Microsoft Outlook the client installed on your PC
• Instructions from here: Outlook 2021 indexing not working - Microsoft Q&A

We need to ensure that Outlook is on the Windows Search Index

• Open Outlook
• Navigate to File --> Options --> Outlook Options --> Search --> Indexing Options
• Make sure Outlook is selected.
• Completely restart Outlook to fix minor glitches that may be affecting the search function.

Outlook items are only indexed when Outlook is open

• Once I opened Outlook and viewed the indexing progress, the number of items pending to be indexed went up, and kept going up for a while. Indexed items started increasing aswell.
• Once the items are indexed, you do not need Outlook open.

Reset Excluded Folders and Rebuild the Search Index

• I did not write this script
• Source: how to delete all exclude folders in search indexer and revert it to default? - Microsoft Q&A
• You can remove the bits from the script that you don't want to perform (Delete database | Reset Folder exclusions).

The following Powershell script fixes a lot of issue with the Windows search and is what I used.

• You can reset everything (exclusions, index database, config) back to default using this PowerShell script. It bypasses the broken GUI and directly clears both the index data and registry entries:
• This will fully wipe the Search Indexer state and restore clean defaults.
• After a reboot, Windows will begin re-indexing only the standard folders.
  • A reboot is not needed, but I did it anyway.
• You should open Outlook now so all of it's emails can get indexed.

# Stop Windows Search Service
Stop-Service -Name WSearch

# Delete the current search index database and configuration
Remove-Item -Path "$env:ProgramData\Microsoft\Search\Data\Applications\Windows" -Recurse -Force
Remove-Item -Path "$env:ProgramData\Microsoft\Search\Data\Temp" -Recurse -Force

# Optional: Reset registry exclusions (set back to defaults)
Remove-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows Search\Gather\Windows\SystemIndex\Sites\LocalHost" -Name "DefaultGatherPolicy" -ErrorAction SilentlyContinue
Remove-Item -Path "HKLM:\SOFTWARE\Microsoft\Windows Search\Gather\Windows\SystemIndex\Sites\LocalHost\Paths" -Recurse -Force -ErrorAction SilentlyContinue

# Start Search Service
Start-Service -Name WSearch

Notes

• If any exclusions still reappear, it means they’re being pushed by a policy or a background process.
• It adds all of the users folders in rather than specifying document and picture folders which is the default configuration of a new Windows PC/Profile.
• This old arrangement that I had (separate Document, Picture, Video folders etc..) listed in the index might of been because my system was upgraded from previous Windows versions (XP --> Win7 --> Win10 --> Win11)

Links

• General
  • Enable or Disable Enhanced Mode for Windows Search in Windows 10 & 11 - MajorGeeks
    • Windows 10 has added many settings to manage Windows Search. By default, Classic mode is on by default, which only searches your libraries and Desktop. The Enhanced mode can search your entire PC.
    • In this tutorial, we help you choose between the two and customize Windows 10 & 11 Search.
  • Weird looking paths get added to Windows 10 search index and break search - Super User
    • A few times in last weeks I have noticed that search from start menu wont find any files. Simply rebuilding the index did not fix this. Looking deeper into indexing settings I found that there was strange looking path being included in the index, one that I had not put there.
    • CSC stands for "Client Side Cache" which is used to hold Offline Files. These are local copies of files that exist on SMB shares like mapped network drives. By default, Windows indexes the CSC so that you can quickly find any network files that you've opened recently. The CSC index can become corrupt and put a full bork on indexing.
• Explorer Crashing
  • Windows Explorer Not Responding But Crashes or Restarts (Windows 11) - Super User
    • Whenever Windows Explorer is opened, it freezes and shows the "App Not Responding" dialogue. Then it crashes or shows the contents of the folder I clicked and freezes afterwards.
    • Solution is to rebuild the Windows Search index
    • This thread also goes through how this solution was reached.
• Rebuild the Windows Search Index
  • how to delete all exclude folders in search indexer and revert it to default? - Microsoft Q&A
    • This has a Powershell and a Batch script method.
    • This is the additional batch file, just in-case it goes offline. I have not used it.

      sc config wsearch start= disabled
      net stop wsearch
      REG ADD "HKLM\SOFTWARE\Microsoft\Windows Search" /v SetupCompletedSuccessfully /t REG_DWORD /d 0 /f
      del "%ProgramData%\Microsoft\Search\Data\Applications\Windows\Windows.edb" /a
      del "%ProgramData%\Microsoft\Search\Data\Applications\Windows\Windows.db" /a
      sc config wsearch start= delayed-auto
      net start wsearch
      :: reg query "HKLM\SOFTWARE\Microsoft\Windows Search\Gathering Manager"
      :: reg query "HKLM\SOFTWARE\Microsoft\Windows Search"
      reg query "HKLM\SOFTWARE\Microsoft\Windows Search\Gathering Manager" /v *path
      reg query "HKLM\SOFTWARE\Microsoft\Windows Search" /v *dir*
      reg query "HKLM\SYSTEM\CurrentControlSet\Services\WSearch"
      icacls %ProgramData%\Microsoft\Search\Data\
      icacls %ProgramData%\Microsoft\Search\Data\Temp\
      icacls %ProgramData%\Microsoft\Search\Data\Applications
      icacls %ProgramData%\Microsoft\Search\Data\Applications\Windows
      PAUSE
      PAUSE

  • How to Reset Windows Search in Windows 11 | NinjaOne - Reset Windows Search to fix slow search and missing results. Use PowerShell, Registry Editor, Control Panel, and other methods to restore search speed.
  • Reset and Rebuild Search Index in Windows 11 | Windows 11 Forum
    • This tutorial will show you how to manually reset and rebuild the search index for accurate search results in Windows 11.
  • How to Delete and Rebuild the Windows 10 & 11 Search Index - MajorGeeks
    • Windows 10 keeps an index of all your searches so that you can get the fastest search results.
    • If you find that you're getting slow, missing, or incorrect results than it might be time to delete and rebuild your search index.
  • How to rebuild Search Index in Windows 11 | TheWindowsClub - You can reset, repair, rebuild Search Index in Windows 11/10 via Indexing Option Control Panel applet or by using this BAT file. Learn how.
• Rebuild the Outlook Search Index
  • How to Rebuild Your Search Index on Microsoft Outlook [TUTORIAL] - YouTube
    • Having trouble finding emails in Outlook? Is your search returning incomplete or incorrect results?
    • It might be time to rebuild your Outlook search index!
    • In this tutorial, we’ll walk you through the exact steps to fix Outlook search issues by resetting and rebuilding the indexing system — a fast and effective way to bring back accurate and lightning-fast results.
  • How to Rebuild the Outlook Search Index (Step-by-Step Guide)
    • Fix Outlook search issues! Rebuild your search index on Windows, Mac, or Exchange to restore accurate and fast search results.
    • This guide provides clear, step-by-step instructions for rebuilding the index on Windows and Mac systems, as well as for Exchange environments.
• Troubleshooting Indexing Issues
  • Fix Windows 11 Indexing Issues: Troubleshooting Guide | Windows Forum
    • Indexing issues on Windows 11 can be as frustrating as a stubborn jam at your favorite coffee machine—especially when you're trying to search for that elusive file during a crunch time.
    • Windows indexing is the unsung hero that catalogs file properties and metadata to ensure speedy searches, but sometimes it just refuses to play ball.
    • If you're encountering the notorious message “Indexing is not running” or noticing that your searches start only to stall mid-air, you're not alone.
    • Here’s a deep dive into why this happens and how you can get your indexing service back on track.
    • Run the Search and Indexing troubleshooter: msdt.exe -ep WindowsHelp id SearchDiagnostic
• Outlook Search Not Working
  • Outlook Search Isn't Working? Here's How to Fix It | How-To Geek
    • Those emails didn't just disappear.
    • Ensure Outlook is on the Windows search index. Open Outlook, then navigate to FIle > Options > Outlook Options > Search > Indexing Options, and make sure Outlook is selected.
    • Completely restart Outlook to fix minor glitches that may be affecting the search function.
    • Try using the Search and Indexing troubleshooter or update Outlook to resolve search-related issues.
  • Outlook 2021 indexing not working - Microsoft Q&A
    • After installation of outlook 2021 all the mails have been downloaded but I am not able to search any mail through search bar. indexing not working after rebuild database.
    • Run the Search and Indexing troubleshooter: msdt.exe -ep WindowsHelp id SearchDiagnostic
• Disable Indexing
  • Does disabling Windows search indexing speed up your computer? - Quora
    • Disabling Windows Search indexing can potentially speed up your computer, particularly if you have a slower hard drive (HDD) or limited system resources. Here are some factors to consider:
  • How to Disable Indexing in Windows 10 & 11 - MajorGeeks - After upgrading to Windows 11, I noticed that my drive was indexed even though I had disabled it previously. Here's how to disable indexing on your hard drive.
• Make Indexing Faster
  • Force Windows indexing to run faster - Office Watch - You can make Windows Search index your documents and Outlook data faster and 'catch up' indexing your documents, pictures and emails.
  • How to Enable or Disable Indexer Backoff in Windows | Windows 10 Forums
    • By default, the search indexer backoff feature will reduce indexing speed while rebuilding the index when there is user activity, and will automatically continue at full speed when no user activity is detected.
    • If indexer backoff is disabled, indexing will continue at full speed even when system activity is high.
• Excluded or Included Folders
  • This Excluded or Included depends on whether you are using the Classic or the Enhanced version of Windows Search.
  • Add or Remove Search Index Locations in Windows 11 | Windows 11 Forum
    • This tutorial will show you how to add or remove locations to be excluded or included in the search index in Windows 11.
    • Microsoft is beginning to roll out a change that brings those two settings pages together so you can easily access to all the Windows Search settings under a single settings page via Settings > Privacy & security > Search. 
  • How to stop Windows Search from auto-excluding repository folders? - Super User
    • Windows search indexer is adding most paths to repository folders (both .git and .svn) to the exclusion list.
    • I can remove them manually of course, but each time I rebuild the index - they are re-added.
    • I can add them as indexed locations, but I'd have to do that each and every time I add a new repository and I add them in varying locations depending on relation.
    • Why is Windows excluding these and how can I alter that behavior?
  • search indexing - How to reset and clear all previous Windows Index config? - Super User
    • This is where Windows Indexing rules (exclusions) are located in the registry, which are not only easier to manage/export/import, but are reflected in Windows Settings awful UX for this:

      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\CrawlScopeManager\Windows\SystemIndex\WorkingSetRules\
      
      and
      
      HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\Gather\Windows\SystemIndex\Sites\LocalHost\Paths\

  • Hide Files and Folders from Search Results in Windows 11 | TheWindowsClub - In this article, we will demonstrate how you can hide files and folders from your Search Results in Windows 11 or Windows 10.