OBJ 3D models are often large in workflows because they store uncompressed geometric data (vertices, faces, UVs) as plain text without built-in compression.
This plain text structure keeps the format widely compatible for editing but uses more space—each vertex’s position, normal, and texture coordinate is a separate line of readable text, which adds up quickly for detailed or high-poly models. Unlike binary formats (e.g., GLB, FBX) that compress data, OBJ prioritizes editability over file size.
If you need smaller files, try merging duplicate vertices in your 3D software or converting to a compressed binary format (like GLB) for sharing/storage, while keeping the original OBJ for editing since it works with most tools.