prevhost.exe
Also called prevhost, preview handler host, preview pane host
Preview Handler Host. Explorer loads IPreviewHandler objects here so a preview crash does not take down explorer.exe.
What you need to know
prevhost isolates preview handlers so a PDF preview crash does not kill Explorer.
prevhost.exe is the surrogate host for Explorer preview handlers. The preview pane loads IPreviewHandler in this process on purpose. explorer.exe stays the shell. Outlook can use the same isolation idea. Ending prevhost blanks the pane, not the desktop.
- Safe?
- Yes. It isolates preview
- Same as Explorer?
- No. Explorer is the shell
- Crash on a PDF?
- The handler died, not the desktop
What is prevhost.exe?
prevhost.exe is the Preview Handler Host. Explorer asks it to load an IPreviewHandler so a PDF or Office preview crash does not kill explorer.exe. It is not Explorer.
What does it do?
It hosts the preview DLL for the selected file type. The folder window, taskbar, and desktop stay in explorer.exe. Search preview is not SearchFilterHost.
Why is it running?
The preview pane (Alt+P) or a similar viewer asked for a preview. Two copies can exist: one low integrity, one for handlers that opted out. No pane means this host should be idle.
Why are there multiple copies?
Two prevhost.exe copies can exist, one at low integrity and one for handlers that opted out. explorer.exe is still the shell, not the preview host.
Is it safe?
Usually safe
System32 prevhost.exe is the Microsoft surrogate. A prevhost.exe in a codec pack is not. A crash here is the preview handler, not proof Explorer is infected.
A legitimate copy normally runs from:
C:\Windows\System32\prevhost.exe
- IPreviewHandler isolation
- Explorer remains explorer.exe
- Low IL by default for handlers
Can I end it?
Preview pane goes blank
Ending prevhost.exe unloads that preview. Explorer should keep the window. That is the opposite of ending explorer.exe, which drops the shell.
Can I remove it?
No
Do not delete prevhost.exe. Turn off the preview pane or remove the bad preview handler. Deleting explorer.exe is also wrong.
Should it start with Windows?
Opening a preview starts it. It is not a Startup Apps entry.
Normal resource behavior
These are contextual labels, not universal averages.
- CPU
- A heavy PDF or CAD preview can spike this host
- Memory
- Follows the handler
- Disk
- Reads the file being previewed
- Network
- If the file is on a UNC path
File information
| Executable name | prevhost.exe |
|---|---|
| Common legitimate path | C:\Windows\System32\prevhost.exe |
| Publisher | Microsoft Corporation |
| Signature expectation | Signed by Microsoft Windows |
Common problems
Preview pane crash loop on one extension
That extension's IPreviewHandler is bad. Explorer staying up is isolation working. Disable the pane or update that previewer.
People restart Explorer for a white pane
End prevhost first. Restarting the shell is a wider hammer than the host was designed for.
Troubleshooting
Diagnose before you change anything destructive.
Alt+P to turn the preview pane off as a test
If Explorer then stays calm, the handler is the bug. Update the PDF or Office previewer. Do not replace explorer.exe.
Note the file type that kills the pane
The handler is registered per extension. SearchFilterHost parsing for the index is a different isolation box.
Technical details
Technical details
| Image name | prevhost.exe |
|---|---|
| Role | IPreviewHandler surrogate host |
Sources and verification
Reviewed by Feex editorial. Last verified August 2026 Status: Feex Reviewed. How we research.
- Microsoft Learn: preview handlers · Prevhost.exe is the out-of-process surrogate
- Microsoft Learn: building preview handlers · Handlers run out of process from Explorer
- Foxhole process map · First-party samples on Windows PCs. Not a lab benchmark.
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