To view stl files online, we Using this 2 websites:
1. STL Viewer Online
https://www.viewstl.com/ View 3D STL files directly in your browser - no software installation is required.
2. Ferma3d
https://ferma3d.ru/viewer/
Open formats: .stl, .obj, .stp, .step, .igs, .iges.
You can use this program for show us your design.