Freeware STL and 3MF viewer - Materialise MiniMagics

 Materialise MiniMagics

Free STL and 3MF viewer

https://www.materialise.com/en/industrial/software/minimagics

...If you’re working with a 3D printing service provider, you need a tool that allows you to view files compatible with 3D printing and communicate efficiently with your account manager. MiniMagics is our free STL and 3MF viewer that allows you to see the same file your account manager sees....