Winamp's Geiss and Milkdrop ported to WebGL
Milkdrop's shader algorithms running in-browser with mic input is genuinely impressive.

Browser audio visualizer when Webamp and dozens of alternatives already exist.
Music listeners, streamers, content creators wanting visualizers
Webamp · Specterr · Vizzy
Milkdrop's shader algorithms running in-browser with mic input is genuinely impressive.
PS1-style CRT visualizer with 20+ modes that runs entirely in browser.
Winamp visualizers from 20 years ago, but in your browser now.
Custom WGSL shaders are cool but 30fps alpha with manual window management limits utility.
Nine thousand pins reacting to FFT data is a fun demo, but it's just another Three.js visualizer.
Clean audio visualizers, but Web Audio API demos already do this.