To make a STL 3D model look small, scale down its dimensions in 3D modeling software (e.g., Blender, Fusion 360) before exporting the STL.
Scaling adjusts the model’s size relative to its original measurements—for example, reducing a 10cm tall object to 5cm makes it visually half as big in viewers or prints.
If using the STL for 3D printing, confirm the scaled size in your slicer tool (like Cura) to fit your print bed—most slicers let you tweak the scale again easily.