To reduce FBX 3D models fast, use optimization tools or software to simplify geometry, textures, and unused data—this cuts file size quickly while preserving usability.
Focus on polygon decimation (lower face count) for geometry, texture compression (reduce resolution or use efficient formats like PNG-8), and deleting unused animations or rigs—these are the fastest ways to shrink size.
For quick fixes, try Blender’s Decimate modifier, Autodesk’s FBX Converter, or online tools like MeshLab. Always save a backup of the original model before making changes to avoid data loss.