File Explorer not previewing pdf files since 25H2 update

Paul Nicholson 560 Reputation points
2025-10-15T08:07:37.1033333+00:00

Since installing the 25H2 update to Windows 11, the preview for pdf files is not working.

I just get the following message "The file you are attempting to preview could harm your computer. If you trust the file and the source you received it from, open it to view its contents"

I have tried everything to restore the preview without success.

Any help would be much appreciated!

Windows for home | Windows 11 | Files, folders, and storage
Answer recommended by moderator
Vivekanandan Tiwari 210 Reputation points
2025-10-20T03:18:02.11+00:00

Here is a simple solution that worked for me -

in the file explorer, just disable this check box as shown in the image, this simply worked for me

(This happened on windows 10 as well!)
Screenshot 2025-10-20 084655

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  1. Sumit 44,316 Reputation points Volunteer Moderator
    2026-07-18T08:55:56.8+00:00

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  2. Jin Hwang 0 Reputation points
    2026-07-13T20:29:56.16+00:00

    For anyone still hitting a completely BLANK PDF preview pane (no error message, no "could harm your computer" warning - just empty) after ruling out the Mark-of-the-Web/25H2 security block and the "Show preview handlers in preview pane" checkbox fix - this may help.

    Re: the highly-upvoted answer suggesting to uncheck "Show preview handlers in preview pane" - that fix does help some people, but it's worth understanding why, because it won't help everyone. Unchecking (and often re-checking) that box forces Windows to rewrite the underlying ShowPreviewHandlers registry value. If that value was missing or in a stuck/inconsistent state, the act of toggling it can clear things up as a side effect - but the setting itself isn't what's actually broken for everyone hitting this. In my case, that checkbox was already correctly checked/enabled the entire time, verified via registry, and toggling it did nothing. So if you've tried that fix and it didn't work, don't stop there - your root cause is likely elsewhere.

    Symptoms that matched my case:

    • Preview pane shows nothing at all for PDFs (not the MOTW warning text - truly blank)
    • TXT/image previews work fine
    • New, locally-created PDFs fail too (rules out Mark-of-the-Web)
    • "Show preview handlers in preview pane" was already checked/enabled
    • Default PDF app doesn't matter - happens with Adobe or Edge set as default

    Root cause, found in two layers: (1) the preview handler CLSIDs had dropped out of the "Approved" shell extensions list, which silently blocks Explorer from loading any handler not listed there - no error, no crash, just nothing rendered; (2) even after fixing that, Adobe's own pdfprevhndlr.dll still failed to render silently (registered correctly, DLL present, correct version - just produced nothing), so I repointed the .pdf preview handler to the generic Windows PDF preview handler instead.

    Here's the PowerShell script that fixes both issues - run as Administrator:

    $fixes=@{'{DC6EFB56-9CFA-464D-8880-44885D7DC193}'='Adobe PDF Preview Handler for Vista';'{3A84F9C2-6164-485C-A7D9-4B27F8AC009E}'='PDF Preview Handler';'{8b40abb8-6c65-465a-8c4b-26224df3125f}'='Windows.Data.Pdf.ProxyStubFactory'}; foreach($c in $fixes.GetEnumerator()){$name=(Get-ItemProperty "Registry::HKEY_CLASSES_ROOT\CLSID\$($c.Key)" -Name '(default)' -ErrorAction SilentlyContinue).'(default)'; if(-not $name){$name=$c.Value}; Set-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved' -Name $c.Key -Value $name -Type String}; Set-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\.pdf\ShellEx\{8895b1c6-b41f-4c1c-a562-0d564250836f}" -Name '(default)' -Value '{3A84F9C2-6164-485C-A7D9-4B27F8AC009E}'; Stop-Process -Name explorer -Force; "RESULT:PASS DETAILS:Approved list updated, .pdf preview handler repointed to generic handler, Explorer restarted"

    What this does:

    1. Re-adds three PDF-related preview handler CLSIDs to the Approved list (they can drop out from certain updates or AV/EDR "hardening" passes)
    2. Repoints .pdf's preview handler from Adobe's (which failed silently in my case) to the generic Windows PDF preview handler
    3. Restarts Explorer so the changes take effect immediately

    If you want to check first before changing anything, here's a read-only version that just tells you PASS/FAIL on each of the three CLSIDs:

    $check=@('{DC6EFB56-9CFA-464D-8880-44885D7DC193}','{3A84F9C2-6164-485C-A7D9-4B27F8AC009E}','{8b40abb8-6c65-465a-8c4b-26224df3125f}'); $approved=Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved'; foreach($c in $check){$present=$null -ne $approved.$c;"$(if($present){'PASS'}else{'FAIL'}): $c"}

    If any come back FAIL, that's your smoking gun - run the fix script above.

    Hope this saves someone the hours of registry archaeology it took to isolate.

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  3. Douglas Bowker 0 Reputation points
    2026-06-11T14:49:21.3866667+00:00

    As of June 2026 it appears this issue may have been (partly) taken care of by Microsoft itself? I'm seeing actual document thumbnails again, which certainly is a big help! *At first I thought the Preview panel was working too but I was mistaken. I also give this problem a better than 50% chance it's an Adobe issue. Acrobat Pro is easily the most bloated piece of software on their entire stable of programs! How can it be that a document app is larger and more complicated than a sophisticated video editor or special fx compositor program?

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  4. Jeremy Brenton 0 Reputation points
    2026-06-11T14:41:15.0633333+00:00

    This worked for me in an elevated Powershell prompt:

    $prog = (Get-ItemProperty HKCR:.pdf).'(default)'

    reg add "HKCR$prog\shellex{8895b1c6-b41f-4c1c-a562-0d564250836f}" `

    /ve /d "{DC6EFB56-9CFA-464D-8880-44885D7DC193}" /f

    taskkill /f /im explorer.exe

    start explorer.exe

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