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. Enric Cortés 39,455 Reputation points Volunteer Moderator
    2025-10-27T13:15:48.1766667+00:00

    Thankfully, there’s a PowerShell script that lets you unblock all files in a specific path.

    In PowerShell, you just need to run the following command:

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

    It will unblock all .pdf files in the downloads folder, including those you plan to download in the future. As long as you trust what you download, this should be good to go. You can run the same script for other paths or file types.

    Saludos,

    Enric

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  2. M_HERMAN 60 Reputation points
    2025-10-27T02:24:42.0766667+00:00

    THIS INSANE "SECURITY FEATURE" IS NOW CAUSING ME POSSIBLY IRREPARABLE HARM!
    I am handling documents for the probate of a will, and I am unable to preview those documents. I do not have the time to open each and every one when I am searching for data. In addition, checking the UNBLOCK box does NOT FIX the preview issue. And I'll just add that these documents are on my non-networked laptop. This "feature" might as well be a North Korean Virus!

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  3. LKG 5 Reputation points
    2025-10-26T18:48:45.07+00:00

    I am running Win11Pro 25H2 - you need one change in group policy to allow downloads without MOTW- gpedit.msc: User Configuration > Administrative Templates > Windows Components > Attachment Manager Setting: Do not preserve zone information in file attachments → Enabled.

    To unlock all files previously downloaded run this as Admin in PowerShell - Replace "D:\Projects\PDFs" with your actual path.

    Get-ChildItem "D:\Projects\PDFs" -Recurse -File | ForEach-Object { Unblock-File -Path $_.FullName }

    If you are seeing an icon instead of your images, check File Explorer, Options, View and uncheck Always show icons, never thumbnails.

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  4. Sunny Surella 15 Reputation points
    2025-10-24T01:19:43.82+00:00

    Below solution steps worked for me:

    A) Currently on Windows 11, version 25H2 for x64-based Systems (KB5070773) (26200.6901).
    B) In Defender:

    User's image

    First-

    1. Check if you are missing PreviewHandlers Registry Key, if yes then use below:

    Method 1) Fix: Recreate the Missing PreviewHandlers Registry Key

    Step 1. Open Registry Editor

    1. Press Win + R, type regedit, and press Enter

    Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer

    Step 2. Create the Missing KeyStep 2. Create the Missing Key
    Right-click Explorer → New → Key.

    Name it exactly: PreviewHandlers

    Step 3. Restore Default Preview Handler Entries Inside PreviewHandlers, create the following String Values (REG_SZ) — you can copy and paste both the names and values exactly:

    Microsoft Office Preview Handler
    {65235197-874B-4A07-BDC5-E65EA825B718}
    Microsoft Office Preview Handler
    {65235197-874B-4A07-BDC5-E65EA825B718}
    Microsoft PDF Preview Handler
    {DC6EFB56-9CFA-464D-8880-44885D7DC193}
    Microsoft Word Preview Handler
    {84F66100-FF7C-4fb4-B0C0-02CD7FB668FE}
    Microsoft Excel Preview Handler
    {00020827-0000-0000-C000-000000000046}
    Microsoft PowerPoint Preview Handler
    {65235197-874B-4A07-BDC5-E65EA825B718}
    Microsoft Outlook Mail Preview Handler
    {A776EDEF-81C0-4A3C-BE0A-46E36A9B8E2D}
    Text Preview Handler
    {1531d583-8375-4d3f-b5fb-d23bbd169f22}
    Image Preview Handler
    {FFE2A43C-56B9-4bf5-9A79-CC6D4285608A}

    (You don’t need all of them; adding the Text, PDF, and Image handlers is usually enough.)

    1. It should look like below screenshot: User's image

    Step 4. Restart Explorer

    Either reboot, or open Command Prompt and run:

    taskkill /f /im explorer.exe

    start explorer.exe

    Then test your preview pane again. If it did not work, then use below solution as well:

    I also used Mark Zuber's suggestion and used below method:

    Method 2)

    Automate It for Multiple Common Folders

    If you want this to apply to multiple folders, use a script like this:
    Open Notepad and paste below code:

    User's image

    $folders = @(

    "$env:USERPROFILE\Downloads",

    "$env:USERPROFILE\Documents",

    "$env:USERPROFILE\Desktop"

    )

    foreach ($folder in $folders) {

    if (Test-Path $folder) {Write-Host "Unblocking files in $folder..." Get-ChildItem -Path $folder -Recurse -ErrorAction SilentlyContinue | Unblock-File

    }

    }

    Write-Host "✅ All files have been unblocked successfully."

    Save it as UnblockFiles.ps1, then run it once as Administrator (right-click → Run with PowerShell). This clears MOTW tags from typical folders where downloaded content lives.

    I hope it will help everyone until Microsoft has a fix for it. The above may not be a proper solution, and may not work for everyone. But is a workaround for now and worked for me.

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