Some update broke the preview of PDFs in Windows Explorer

[spoolin01]

Back around October, apparently a security update broke the preview function in Windows Explorer for Windows 7, 10, and 11. I fixed this on my Win10 laptop but don't recall now what all I did. I'm about to dig into this for Windows 7 now. Anyone have a handy method or source to fix this in batch fashion, both for new and existing downloaded PDFs?

ETA: I found this PowerShell command to unblock all files within the target folder:

Set-Location -Path "<folder path>"
Get-ChildItem -File -Recurse | Unblock-File

Replace <folder path> with the folder path (e.g. D:\my folders\targetfolder). Requires PowerShell 3.0 or higher for the Unblock-File command. I used 3.0.

 

[torchwood]

actually 2 settings
when you view/preview a new pdf it generally opens a new window in your browser.... so thats a browser setting
for downloaded pdfs it will depend on which Reader program you have... ie Adobe

 

[spoolin01]

actually 2 settings
when you view/preview a new pdf it generally opens a new window in your browser.... so thats a browser setting
for downloaded pdfs it will depend on which Reader program you have... ie Adobe

I'm just dealing with the Windows Explorer preview function, not browser viewing. There is some sort of flag that is added to internet downloads apparently (MOTW) Mark of the Web - Wikipedia and an October 2025 update changed the handling of these to prevent previewing, over some sort of security concern. There are a couple of ways to change this policy back or reverse the flagging for the next files you download, but the damage to existing downloads was already done. I found the above PowerShell commands to allow batch unblocking of existing files at the folder level. It may need tweaking to work for sub-folders, I haven't tried yet.