What are 3D model loaders?

glTF (GL Transmission Format)

Where possible, we recommend using glTF (GL Transmission Format). Both .GLB and .GLTF versions of the format are well supported. Because glTF is focused on runtime asset delivery, it is compact to transmit and fast to load. Features include meshes, materials, textures, skins, skeletons, morph targets, animations, lights, and cameras.
Public-domain glTF files are available on sites like Sketchfab, or various tools include glTF export:
When glTF is not an option, popular formats such as FBX, OBJ, or COLLADA are also available and regularly maintained by many libraries.