Microsoft kills File Explorer Preview Pane, but why?

[Mayank]

You’re not alone if you see a security alert when previewing PDF or other documents/files in File Explorer: 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

When the October 2025 Update for Windows 10 (KB5066791) and Windows 11 (KB5066835) shipped, we noticed that File Explorer’s Preview Pane stopped working. This was very odd. I mean, you can still turn on Preview pane from the options menu (see the screenshot below), but it’ll not be able to preview downloaded files.

If you try to preview the files, let’s say, a PDF, it’ll display a security alert: The file you are attempting to preview could harm your computer. If you trust the file and the source you recieved it from, open it to view its contents.

See the screenshot below. I can no longer view the file I downloaded from an external source. In this case, I downloaded the file from SharePoint:

But what about the PDFs I created on my PC? They still load.

Turns out it’s NOT a known issue. But it’s a feature. Microsoft disabled the Preview pane in File Explorer for download files to limit potential security risks.

The reason behind this move is to stop possible leaks of NTLM credential hashes when previewing downloaded files. When Explorer tried to show a preview of a file, it could indirectly allow the system to send sensitive authentication data to remote servers.

MIcrosoft’s solution is to disable previews in Explorer. This will prevent the attack method.

You can turn off this security feature by modifying your registry, but I don’t recommend doing that. Instead, if you trust the folder where you save your downloaded files, you can just unblock it by running the following script in PowerShell:

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

Let me know if you’ve a question. I’ve asked Microsoft for more details, but for now, this is the only workaround.

As for other issues in Windows 11 October 2025 Update, Microsoft confirmed LocalHost problems are fixed via a server-side patch. For Windows Recovery issues, we’ve a new emergency update (Windows 11 KB5070773).

Are you aware of other issues in the update?

[user2]

Hi, I have NEVER done anything in a powershell but I’m desperate to unblock my PDFs! I got this far and as far as I know, it’s not working, can you help me?

[Mayank]

where do you want to unlock your PDFs? if you can share the folder path, i can help.

[user2]

In file explorer preview pane, how do I share that with you?

[user2]

I assume that’s where they need to be unlocked, as you can tell I’m new at this!

[Mayank]

You get the directory path location like this:

[user2]

This is what mine shows, it’s not the C:\…, it’s the first folder in my downloads, am I doing it wrong?

[Mayank]

Unblock-File -Path “C:\Users\mayan\downloads*.pdf”

In this case, mayan is my username.

You have to replace it with your username

Go to C drive

Open Users folder

You’ll see a folder name you will recognise

That’s your username.

If you still don’t get it, I am going to update the story with new instructions, and better solution than doing this.

Please wait few hours.

[user2]

First I want to thank you for walking me thru this, I’m sure you didn’t sign up to tutor a newbie like me! And if I take up too much of your time, it’s completely fine to cut me loose!

Here’s what my users looks like, not sure which one to click

[Mayank]

Sorry, took me a while. I went ahead and added more details to our article:

Microsoft admits File Explorer Preview pane won't work in Windows 11 25H2 for...

Does it help?

To find user profile folder name, just open PowerShell and run echo $HOME

Still willing to help you out. Let me know your questions (we’re ALL beginners at some point!)

[TechForceAdmin]

Similarly to “user2” I am not super familiar with PowerShell, but I was able to use your full article to fix the issue for a client’s Downloads folder. I could not, however, fix the issue for their shared “Scans Folder”, which is (I believe) a shared file folder stored on their G: drive/server. I tried several different things, including Unblock-File -Path “G:\Scan Folder\*.pdf”, but with no success. Would I have to run it on the server for it to work, and is that a bad idea? When viewing the file properties of a .pdf from that folder the “Unblock” checkbox isn’t even there, so I know that the nature of the folder is doing something to complicate the issue.

Any advice you can provide would be GREATLY appreciated!

[Mayank]

@TechForceAdmin - Hey. I understand PowerShell can be complicated. I’m a PowerShell dev and I can try to help you.

But basics first. don’t run Unblock-File on the server. Your “Scans” share isn’t an Internet-downloaded file scenario, so there’s nothing to “unblock,” and doing it on the server won’t change what File Explorer thinks about a remote path.

Basically, Windows’ new behavior treats remote locations more strictly for previews. Mapped drives like G: (SMB/UNC) can be seen as Internet unless you mark the server/range as Local intranet. That’s why Preview is blocked even though there’s no MotW (MotW = inyternet downloaded files).

I recommend that you mark the file server as Local intranet (if you trust the server, it is safe thing to do):

1. Press Win + R > inetcpl.cpl.

2. Security tab > Local intranet > Sites.

3. Check Automatically detect intranet network (and/or Include all network paths (UNCs)).

4. Click Advanced… and add your server or IP range, e.g.:

   • \\fileserver (sometimes you must use the FQDN)
   • or 192.168.1.*

After changin, close all Explorer windows (or restart Windows) and reopen File Explorer.

I also have a POwershell script you can use if you don’t like the above approach (since you are not familiar with PowerShell, I’d recommend that you follow the above method):

$k = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Ranges\Range1"
New-Item $k -Force | Out-Null
New-ItemProperty $k -Name ":Range" -Value "192.168.1.0-192.168.1.255" -PropertyType String -Force | Out-Null
New-ItemProperty $k -Name "file" -Value 1 -PropertyType DWord -Force | Out-Null

• Add a named host (if you use a DNS name/FQDN):

$host = "fileserver"   # change to your server name or FQDN
$k = "HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\$host"
New-Item $k -Force | Out-Null
New-ItemProperty $k -Name "file" -Value 1 -PropertyType DWord -Force | Out-Null

(second potential workaround):

If you can’t change zones as I highlighted above, you need to copy copy to a local folder. (e.g., to Downloads\Scans) and preview there.

$src = "G:\Scan Folder"
$dst = Join-Path $HOME "Downloads\Scans"
robocopy $src $dst *.pdf /XO /R:0 /W:0

Preview works locally because there’s no “remote” classification., but I understand it defeats the purpose of quickly viewing files from the server in your File Explorer. So maybe, try changing the zones?