No 3D preview. You need to export to FBX/OBJ to view models externally. 3. DevX Unity Asset Viewer (Online / Web-Based) Platform: Any browser Cost: Freemium
Noesis is not a Unity-specific tool, but it supports dozens of game formats, including many Unity container files. It excels at with full texture mapping and animation playback. unity3d file viewer
If you have the actual Unity project source files (not a compiled game), the Unity Editor itself is the best viewer. You can open .unity scene files, inspect GameObjects, view shaders, and run the game in Play Mode. No 3D preview