An OBJ viewer is a software tool that allows users to view and manipulate 3D models in the .obj file format. This file format is commonly used in 3D modeling and visualization, making it essential for designers, architects, and engineers. With an OBJ viewer, users can easily rotate, zoom, and pan around 3D models, giving them a better understanding of the object's structure and aesthetics. Additionally, OBJ viewers often support texture and material rendering, providing a more realistic representation of the 3D model. Some advanced OBJ viewers even support animations and shader effects, allowing for dynamic presentations of the 3D models. Overall, an OBJ viewer is a valuable tool for anyone working with 3D models, providing an intuitive and interactive way to explore and showcase their designs.