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. KEVIN 0 Reputation points
    2026-03-09T17:41:21.58+00:00

    The initial solution I had that worked was deleting the update that has been mentioned multiple times but the problem returns with every security update a solution was posted to change a key in the registry this works fine until the next security update that resets it but I have found this easier than turning off updates the key as I copied and now store as a note on computer is
    In Registry Editor (search regedit in taskbar), navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3.

    Look for key 180F , double click on it and change its value to 0 (if present).

    Hope this helps fellow suffers!

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  2. Dave Rhodes 0 Reputation points
    2026-03-05T12:41:06.8233333+00:00

    I had this issue for one user when previewing local files in explorer.

    I found that the following Regkey was missing

    Computer\HKEY_CLASSES_ROOT.pdf\ShellEx{8895b1c6-b41f-4c1c-a562-0d564250836f}

    This should contain a key called "default" with the following value. {DC6EFB56-9CFA-464D-8880-44885D7DC193}

    On top of this the preview handler need to be set correctly.(HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers 

    • Name: {3A84F9C2-6164-485C-A7D9-4B27F8AC009E}
    • Data: Microsoft PDF Previewer

    Once this was put back in place and Explorer restarted via Task-manager the Explorer PDF previews worked again.

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  3. Mahyar 5 Reputation points
    2026-02-25T15:42:49.9866667+00:00

    For files on your network, you can use "Internet Options" and add your network drive to the trusted sites. This worked for me.

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  4. Brett T 5 Reputation points
    2026-02-12T22:14:48.5466667+00:00

    This seems to work:

    Run Group Policy Editor (search for gpedit)

    User Configuration > Administrative Templates > Windows Components > Attachment Manager

    Double click "Do not preserve zone information in file attachments"

    Click Enable, Apply

    That seems to be enough, but you can also double click "Inclusion list for moderate risk file types", Enable, type ".pdf" in the box, and Apply

    **This only works for files you download from now on. Use this powershell command (run as administrator) on any folder with existing pdf's you can't preview:

    Get-ChildItem "C:\Users\user\Downloads" -Filter *.pdf | Unblock-File

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