I guess it is https://asciinema.org https://asciinema.org but their samples have centered full screen. Maybe a CSS issue here. I'm not sure about the point eit

I guess it is https://asciinema.org https://asciinema.org but their samples have centered full screen. Maybe a CSS issue here. I'm not sure about the point either. Maybe if you embedded a small player it would be zoomed out and fullscreen would show the native style.