This library builds upon pygfx and wgpu-py. Unfortunately, the latter doesn't support running on WASM, pyscript or pyodide yet, but there's an issue about it:

https://github.com/pygfx/wgpu-py/issues/407

PRs welcome though :-)

That's because WebGPU is still experimental. This will change, as it's set to replace WebGL.

Fastplotlib / pygfx are primarily meant to run on desktop. When using it via the notebook the server does the rendering.

As Ivo said, we have plans to support running in the browser via Pyodide, which opens some interesting things, but is not the primary purpose.