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File Explorer not previewing pdf files since 25H2 update

Paul Nicholson 545 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

79 answers

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  1. Jerimy Orr 10 Reputation points
    2025-10-21T17:41:56.0266667+00:00

    I had the same issue as InchCreations, but once I checked the Unblock option box, saved then opened the file, moving forward I could preview it. It's incumbering but effective, for now.

    2 people found this answer helpful.
  2. 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.

    2 people found this answer helpful.
  3. Gee Wizard 10 Reputation points
    2025-11-25T04:14:57.4033333+00:00
    2 people found this answer helpful.
    0 comments
  4. Nic J 15 Reputation points
    2025-12-04T06:15:13.87+00:00

    Just reading all the posts there seem to be 20 different ways to fix this issue ..My personal view is ... I did nothing to cause this issue and should do nothing to fix it either. MS should send a patch at the next update to sort this out once and for all !!

    2 people found this answer helpful.
  5. Ramesh Srinivasan 173.7K Reputation points Volunteer Moderator
    2025-10-15T10:08:04.63+00:00

    Hi Paul,

    In that case, here are some options that I can think of.

    After saving the PDF from email to a folder, right-click on the PDF file, click Properties, select "Unblock", and click OK.

    -or-

    Create a scheduled task that executes the above PowerShell command at regular intervals to bulk unblock PDFs.

    -or-

    Create a scheduled task that executes the Streams.exe tool (from Sysinternals) at regular intervals to bulk unblock PDFs.

    Streams - Sysinternals | Microsoft Learn

    How to Bulk Unblock Files Downloaded from Internet

    Streams command-line example:

    c:\tools\streams.exe -s -d %userprofile%\downloads\

    The above command unblocks all files in the Downloads folder and subfolders.

    -or-

    Or, put all those PDFs in a FAT or exFAT partition. This may not be a feasible option for many users due to lack of security, but posting it anyway.

    1 person found this answer helpful.
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