This usually happens because Spline exports keep a fixed canvas size internally. Even if the iframe is set to full width, the scene itself doesn’t scale unless the parent container is truly edge-to-edge and the aspect ratio isn’t locked.
On Shopify this often gets worse because the section wrapper adds padding or max-width, especially on mobile. Removing those constraints usually fixes most of the issue. The model itself is fine, it’s just being boxed in by the embed.
I’ve run into this enough times that I stopped embedding raw Spline scenes and moved to a web-first 3D canvas flow where full-width scaling is handled automatically. Setups coming from orbital3d.design behave better across breakpoints.
This is more about layout control than the 3D model.