Papa’s Best STL Thumbnails

A shell extension that adds preview thumbnails for STL files to Windows Explorer. Runs on Windows 7 or later.

Papa’s Best STL Thumbnails displaying a folder with random STLs from thingiverse



Thumbnail generation is based on the fastest STL viewer available. Folders full of STL files are no problem, and most STL thumbnails are generated as fast as those of JPG photos.



Papa’s Best STL Thumbnails display countless STL variations, even where other programs fail:

Installation for all users

Papa’s Best STL Thumbnails installs for the current user by default. To install it for all users on a system:


No thumbnails showing up

Ensure thumbnails are generally enabled. Are thumbnails working with other file types on your system, e.g. photos? If not, you may have disabled them altogether.

Is User Account Control (UAC) disabled? UAC is not only a strong protection against malicious software, it also properly isolates user accounts from one another. Since the STL Thumbnails install in a user context, they may not run properly with UAC disabled. If you are absolutely sure about keeping UAC disabled, perform an installation for all users.

Clear your thumbnail cache. This forces Explorer to request new thumbnails instead of relying on outdated data.

Download my diagnostic tool. It mimics the way Explorer requests thumbnails, and may point at the issue.

Dark background on some thumbnails

a folder with two thumbnails whose background is entirely black

Clear your Explorer thumbnail cache (via the drive cleanup) or copy the file to a different location.

This is a bug in Windows 10 that also affects other thumbnails – for example transparent PNG images here and here.

I can’t do anything in my program to work around it, I’m afraid. Please use the Windows 10 feedback function to report this to Microsoft. If enough users do it, they may eventually fix it. Windows 7 does not have this bug.

Something Missing?

Encountered a problem? Have a suggestion? Let me know: