HOW DO I REMOVE THE SECURITY FEATURE TO PREVIEW PDF DOCUMENTS IN FILE EXPLORER?

Leesa Beirold 0 Reputation points
2026-09-16T19:45:57.8733333+00:00

I just got a new computer and it does not allow me to preview documents in file explorer. To be able to preview, I have to go into the three dots ... next to VIEW, Click on PROPERTIES, scroll to Attributes then click "UNBLOCK". I have to do that for every single file. Is there a way to make UNBLOCK the default for all documents?

Windows for business | Windows 365 Business
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  1. Marcin Policht 108.5K Reputation points MVP Volunteer Moderator
    2026-09-16T20:40:47.4666667+00:00

    Windows marks downloaded files with a “Mark of the Web” alternate data stream (Zone.Identifier). To stop having to manually click Unblock, you must either remove that marking automatically or prevent it from being created.

    On Windows Pro or higher, open Local Group Policy Editor and set “Do not preserve zone information in file attachments” to Enabled under User Configuration > Administrative Templates > Windows Components > Attachment Manager. This prevents Windows from adding the Zone.Identifier stream to newly downloaded files.

    On Windows Home, use the registry instead. Run:

    Windows Command Prompt

    reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments" /v SaveZoneInformation /t REG_DWORD /d 1 /f

    Then sign out and back in. This sets Windows to not store zone information for future downloads.

    For files already downloaded, you can bulk remove the block using PowerShell:

    PowerShell

    Get-ChildItem "C:\Path\To\Folder" -Recurse | Unblock-File

    Or for a single file:

    PowerShell

    Unblock-File "C:\Path\To\File.ext"

    Be aware that disabling zone information reduces security because Windows will no longer warn you about files downloaded from the internet.

    If the above response helps answer your question, remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

    hth

    Marcin

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  2. AI answer

    2026-09-16T19:46:09.3266667+00:00

    Windows now blocks File Explorer preview for files marked as downloaded from the internet by default. This behavior started with Windows security updates released on and after October 14, 2025, to reduce NTLM hash leakage risk from unsafe file previews.

    There is no supported setting in the provided documentation to make Unblock the default for all downloaded files automatically.

    Supported ways to allow preview are:

    1. For an individual downloaded file:
      • Right-click the file in File Explorer.
      • Select Properties.
      • Select Unblock.
      • Sign out and back in if the change does not take effect immediately.
    2. For files on an Internet Zone file share:
      • Open Internet Options.
      • Go to the Security tab.
      • Add the file share address to Local intranet or Trusted sites.

    Warning: adding a file share to Local intranet or Trusted sites relaxes security for all files from that share.

    If the issue is only that the preview pane is not visible, also verify File Explorer preview is enabled:

    • In File Explorer, open View and select Preview pane.
    • In File Explorer Options > View, ensure Show preview handlers in preview pane is selected.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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