Why OBJ 3D model is broken animation in compatibility?

OBJ 3D models have animation compatibility issues because the OBJ format doesn’t natively support animation data like keyframes, skeletal rigs, or bone weights. OBJ is designed for static 3D geometry (vertices, faces) and basic material links (via MTL files)—it can’t store the dynamic data needed for animations (e.g., how a character’s arm moves with bones). When you save a rigged/animated model as OBJ, that animation data gets stripped, so importing it into another tool leaves no data to play back, resulting in broken or non-functional animations. If you need to preserve animation, use formats like FBX or glTF instead—they retain rigging and keyframe data, ensuring your animations work consistently across different software.