How can i use this?

[Kr666you]

I want host nostalgist.js on my pc so i can play games from localhost instead of the nostalgist.js website.
I also want to run this on a circuitpython device (it is an raspberry pi pico w).

[arianrhodsandlot]

Nostalgist.js is a library for programmers rather than a product for end users. You might need to implement a HTML page with frontend technologies for selfhosting.

If you are not familiar with frontend programming, you can also download the official RetroArch web build here: https://buildbot.libretro.com/stable/1.17.0/emscripten/ , then extract the RetroArch.7z and selfhost the extracted folder, though it's not powered by Nostalgist.js.