Finder preview – just universal thumbnail (for JPG, PNG, PDF, etc)

I've got it!

It was something from Google Drive, that blocked the system-wide icons generating!

After reinstalling Google Drive and allowing it to use System software and after the following restart are all the icons back!

I've noticed in an discussion forum, that some people had icons blocked by Dropbox and somebody mentioned Google too, but I didn't pay attention to it.

All in all, thanks for your assistance, BDAqua, you've taught me some new things.

Take care, pal!

Greetings from Czechia, EU

Thanks BDAqua,

Safe Boot was one of the first measures, I've tried (as shown in the list in the beginning of this thread).

I've performed the Terminal commands from your response with results as follow:

• • The initial problem with generic icons persists
  • All (or at least most of) the Apple apps have lost their specific icons (Dock and Last items menu) and were replaced by generic apps icon
  • After restart they reappeared, except Messages.app

The strangest thing is, that – from the very beginning – there are a few icons, that have kept their image content thumbnail (all of them JPGs), but the rest keep their app generic icon.

I've migrated system from a backup in dozens times, but this is the first time, I'm experiencing the icon problem.

Hi BDAqua,

in my original post, I've written:

In addition, I've also tried another user with admin rights and moved some of affected documents to Users/Shared, but without any progress.

In other words – it doesn't work in a new account either.

I also tried to copy other files – it's the same – just generic thumbnails. When I create a new document (e.g. screenshot or a duplicate of existing image) it's got also just the generic preview.

Those few, that already had the right thumbnail, keep it also in another user.

So it seems to be that the problem is on system level.

I've even reinstalled the system in the meantime, but it didn't changed the crucial behavior. It's probably somewhere in the system QuickLook library file.

I need to stay on Mojave, because of Adobe CS6.

Thanks for a suggestion,

I remember Graphic Converter (GC) from the old days of Mac OS 7–9 in mid/late 90's.

I tried it, but it will not help in this case

– in GC everything looks OK

– in Finder, everything looks not OK, even the newly converted files by GC have just generic icons

– restart will not change anything

This is not a solution, especially for PDFs

I don't know what's wrong, that system will override even the re-generated stuff from GC.

Many times… A few times to Safe Boot.

Still the same generic icons.

On my other computer I see everything OK. When I copy the files from there, everything changes to generic icons – no matter how many times I restart.