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. Devendra Panchal 0 Reputation points
    2025-10-17T12:52:12.57+00:00

    Thank you all for the various ways to solve this issue.

    One possible solution I found is that if the PDF version of the PDF file that was generated in should be 1.7 (8.x) or higher. The PDF version is mentioned within the PDF -> Menu -> Document Properties.

    Everything else remaining the same, 8.x, works with the preview.

    If your PDF doc ver is below 1.7 (8.x), print that same file to a PDF from your computer, and that new copy should become 8.x and poof - the preview works.

    Print To PDF and Save As - are they both same? - that remains to be seen.

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  2. Kirill P 55 Reputation points
    2025-10-17T15:05:57.5366667+00:00

    After applying this solution, Windows will stop showing the "security warning" when you try to open files downloaded to your Downloads folder.

    Step 1: Unblock all already downloaded PDF files. Open PowerShell as Administrator and run:

    Unblock-File -Path "C:\Users\admin\Downloads\*.pdf"

    Replace admin with the actual path where your files are downloaded. Usually, it's your user folder on drive C. You can check your exact user path by running this command in PowerShell:

    $home

    Step 2: Prevent Windows from setting the "file is blocked" flag for newly downloaded files. Open Registry Editor (Win + R > type regedit) and navigate to:

    Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\

    Create a new key named Attachments. Inside it, create a new DWORD (32-bit) value called SaveZoneInformation and set it to 1.

    Or paste this in PowerShell:

    New-Item -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments" -Force | Out-Null
New-ItemProperty -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments" -Name "SaveZoneInformation" -PropertyType DWord -Value 1 -Force | Out-Null

    Alternatively, you can do the same via Group Policy Editor (Win + R > type gpedit.msc): User Configuration > Administrative Templates > Windows Components > Attachment Manager > Do not preserve zone information in file attachments > Enabled

    Step 3: The same issue can happen when opening PDFs from shared network locations. In that case, do the following: Press Win + R, type inetcpl.cpl, and open the Security tab. Select Local intranet > click Sites > check Automatically detect intranet network. You can also click Advanced, then add the required network IP range manually — for example: 192.168.1.* > click Add.

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  3. Patricia Weaver 0 Reputation points
    2025-10-17T17:48:32.4033333+00:00

    I found out how to fix it -

    In your file explorer, right-click the file and select properties:

    image

    Under General, in the bottom - Security - check "Unblock"

    User's image

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  4. Jam Z 0 Reputation points
    2025-10-17T21:07:50.85+00:00

    This error appeared following the security update. My google drive files could not be previewed.

    Few things to try to fix it from ChatGPT that worked for me:

    1: Remove the “Internet Zone” tag for all Google Drive files

    You can safely delete the Mark-of-the-Web tag from your Google Drive folder so previews work normally.

    Run PowerShell as Administrator, then paste this:

    Get-ChildItem "G:\My Drive" -Recurse | Unblock-File

    Replace G:\My Drive with your actual Google Drive path.

    1. (Adobe users)

    Open Adobe Acrobat Reader.

    Go to Edit → Preferences → Security (Enhanced).

    Uncheck Enable Protected Mode at startup (you can re-enable later).

    1. Restart File Explorer and test again.
    2. Add Google Drive’s mount path to Windows’ Trusted Locations

    Open Control Panel → Internet Options.

    Go to Security → Local intranet → Sites → Advanced.

    Click Add, and add:

    file://localhost/G:\

    (Replace G:\ with your actual Google Drive letter — check in File Explorer.)

    Click Close → OK → Apply.

    Hope this helps

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