File explorer: PDF's preview showing "INDEX OF" in network folders

Question

Hi,

This issue started today at work on several computers on both Windows 11 and Windows 10. Could it be related to a recent Windows update?

Pdf files (and only PDF's) previews aren't working in any network folders, Instead of showing the file preview it shows "INDEX OF:"

Previews work normally for excel, word, etc.

Weird stuff.

Answer 1

I wanted to report that I have found the issue.

If the path to the file or the filename itself contains a pound sign # it looks like the previewer might be disregarding all the path that comes after the pound. Removing the # solves the issue.

If the # is the first character of a folder or a file, the previewer will show you the index of the folder.

If the # is in the middle of the file, the previewer will throw an error

I suspect like the previewer is not escaping the # character and therefore treats all characters after it as if it was a commentary, like when you write comments while programming.

I tested it with multiple machines and the same problems are happening on all of them. So far none of the updates I uninstalled seemed to have solved the problem.

This totally looks like a bug on the previewer.

Answer 2

I have found the cause and a solution to this over on the Foxit forms. The problem is that the Microsoft PDF Previewer keeps taking over the preview pane and the Microsoft PDF Previewer has a bug where it cannot load a preview of files containing the # symbol. I'm not sure if the Preview Handler takeover happens during Windows updates or when but its very annoying. For one of my clients, I've had to run a script via Task Scheduler when the user logs in to make sure the issue doesn't come back.

Solution:
Change the "[HKEY_CLASSES_ROOT.pdf\ShellEx{8895b1c6-b41f-4c1c-a562-0d564250836f}\Default" key from {3A84F9C2-6164-485C-A7D9-4B27F8AC009E} which is MS PDF Previewer to {1B96FAD8-1C10-416E-8027-6EFF94045F6F} which is the Foxit PDF Preview handler.

If you don't use Foxit, you should be able to find your preview handler here: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers
Then copy the value of your preferred preview handler and use that instead.

Here is the simple .bat script I wrote to do this:

@echo off

REM Check if Microsoft PDF Previewer took over the preview pane.
for /f "tokens=3" %%a in ('reg query "HKCR.pdf\ShellEx{8895b1c6-b41f-4c1c-a562-0d564250836f}" /VE ^|findstr /ri "REG_SZ"') do if %%a=={3A84F9C2-6164-485C-A7D9-4B27F8AC009E} (goto Fix) else (exit)

:Fix
REM Check for Admin.
if not "%1"=="am_admin" (powershell start -verb runas '%0' am_admin & exit /b)
REM Fix preview pane - set it to work with Foxit Phantom PDF
REG add HKCR.pdf\ShellEx{8895b1c6-b41f-4c1c-a562-0d564250836f} /ve /d {1B96FAD8-1C10-416E-8027-6EFF94045F6F} /f
REG add HKCR.pdf\ShellEx{8895b1c6-b41f-4c1c-a562-0d564250836f} /v PrevPreviewHandler /d {1B96FAD8-1C10-416E-8027-6EFF94045F6F} /f
exit

I hope this helps.

Answer 3

why cant you just FIX THE PROBLEM, WHY DOES MICROSOFT HAVE TO BE SO HARD TO USE. DO YOU GO TO MEETINGS WITH BILL GATES AND HE TELLS EVERYONE MAKE IT DIFFICULT?? MAKE **** CHANGE EVERY GD TIME??????????????????????????? iM SO SICK OF THIS .....

Answer 4

Thanks Carlos. Yes for us it's related to having a # in the path as well...unfortunately changing a bunch of network folder names isn't an option right now.

Someone on another website said that he updated Adobe yesterday and it worked but today the issue came back.

We are using Foxit and I updated it a few hours ago and it works here as well but I wonder if it will keep working. Hopefully it does.

Answer 5

Hi, my name is Anderson Souza, I hope I can help you with your issue.

How is the distribution of updates done there in your company? Does each machine update itself directly from the Internet or do you use WSUS? I recommend that you check for the latest update applied on one of the workstations and remove it to test if this may have actually been the case, as it happened on several machines at the same time, this is very likely the problem.

You can go to Start > Settings > Update & Security > "View update history" to check the updates applied to your system just before the issue starts to happen.

Note that there are several update categories that can be expanded or collapsed by clicking the arrows on the left side of each one (Feature Updates, Quality Updates, Driver Updates, etc).