Guy, when i use Unity GLTF for export gltf file from unity file then gltf file bigger than fbx file fist, this is so bad, any one have some other lib ?
I would not expect any converter or authoring tool to output optimized files. If you can find a converter that gives correct visual results, you’re doing better than most — use that! Then use something like glTF Transform or gltfpack to optimize the file afterward.
If you’re still having trouble, perhaps you could share the two files and we can inspect what’s causing the size difference.