how to change extension-specific handlers for Explorer's Preview Pane?

June20 · 24 Jun 2020

In the Explorer view, I normally have the file list in Details format and the Preview Pane turned on.
A few associations have recently become broken, in that the preview pane shows nothing, but file with other extensions show their normal previews.
All other Explorer functions are behaving normally. I don't know what has done this, perhaps bugs in the uninstall process for a few apps.
Changing the default app used to open the file (as set by the Rclick/Opens with dialog box) makes no difference to whether anything shows in the Preview Pane.
The handler chosen to create the preview is presumably located in the registry, but I can't see how the system works.
So how do I permanently change the preview handler for a given extension?
What is the correct key/value structure for each file association in the registry to make this work?

Version is Win10 Pro 1909 build 10.0.18363.836

dalchina · 25 Jun 2020

Hi, How do you change/set those?

Perhaps you could quote a couple of example file types, and the program you have assigned as default for them.

I collected this which may be of interest:

Previewing a file type requires a preview handler (preview filter) to be registered, and certain registry settings for a given file type to be appropriate.

How to add preview for a file type manually:
Enable Previews for new file extensions | Annoying stuff I figured out (or am trying to)

This is for developers:
https://docs.microsoft.com/en-us/windows/win32/shell/how-to-register-a-preview-handler

To add preview for a file type use:
PreviewConfig (v1.2) for Windows 7/Vista
https://tweaks.com/windows/39264/expand-explorer-preview-pane-with-previewconfig/

Preview Handler association Editor
Free Download: Preview Handler Association Editor to Group Same Type of File with Different Extensions - Tech Journey

Note: these list registered handlers.

Doc, docx, xlsx :
Libre Office does not add file type handlers for these. MS Office does.

idgat · 25 Jun 2020

June20 said:

So how do I permanently change the preview handler for a given extension?

Right-click on the file name > Open with > Choose another app (Do this irrespective of whether the target app is already listed or not) > navigate to the app > tick the box Always use this app to open .. etc > OK

Alternatively, Windows 10 Settings > Apps > Default Apps > Choose default app. by file type > etc, just follow the promtps.

Once the default app is (re)set for that file type, previews should be available in File Explorer.

dalchina · 25 Jun 2020

Only if there's an appropriate preview handler registered for that file type.

I had hoped that would be clear from my post #2

For example, I have doc, docx associated with Atlantis Word Processor. I also have Libre Office installed.

However, there is no preview of those file types as there is no preview handler for those types provided by either.

Whether you get a preview or not depends on
a. whether it's a file type native to Windows e.g. txt, rtf
b. which programs you have installed and which preview filters they provide

June20 · 25 Jun 2020

Dalchina, thanks for the suggestions - I will try these out soon.

Idgat, if you read my post you will see that I say, explicitly, that what you suggest doesn't work. I think it's likely that some registry keys have been corrupted or deleted and cannot be fixed using the basic entry-level GUI methods. I should also make it clear that I am not trying to install new apps: merely trying to restore the preview - using any one of the apps that are installed and still exist. For example, my Preview Panel works for PDFs, but not for JPGs - even though the "Open with" list for JPGs includes Photos, Win Photo Viewer, Irfanview, and others. I would be happy if the Preview Panel used any one of these, but it shows only an icon for the current default app, with no actual preview image. Because the icon changes with the default setting, it is clear that the system knows the path to the default app: but it won't generate the image.

dalchina · 25 Jun 2020

If it helps, there is a tutorial allowing you to set the default for a lot of file types should that be relevant.

A useful trick can be to compare when logged in as a user newly created for test purposes.