From Winamp to WebAssembly
MilkDrop was Ryan Geiss’s visualizer for Winamp: beat-reactive equations rendering fractals, waves, and warping geometry, with a preset format (.milk) that a community spent two decades writing art in. projectM reimplemented it as open source; Butterchurn brought it to WebGL. Groovalizer builds on projectM compiled to WebAssembly, so the real engine runs in a browser tab at 60fps.
Nothing installs, and your audio never uploads: analysis and rendering both happen on your machine.
What Butterchurn can’t do
Butterchurn is a beautiful, free, open-source MilkDrop player, and that’s all it sets out to be. There are no accounts, no editor, and crucially no export: if you want a video of what you saw, you screen-record it, capturing compression artifacts, dropped frames, and your notification sounds along the way.
Groovalizer treats the video as the product. It renders offline, frame-by-frame, synced to your uploaded track, and encodes MP4 (or WebM) at a steady frame rate, in widescreen for YouTube, vertical for TikTok and Reels, or square for Instagram.
On top of the engine it adds the tooling a player never needed: a looks list with search and Surprise me, a .milk code editor with live reload, controls for how strongly a look reacts and how fast it moves, and Song parts that give different sections of a song their own looks.
Projector mode, like the old days
The other half of the MilkDrop tradition is live: visuals on a wall while music plays in the room. Groovalizer’s Go Live mode listens to your microphone or line-in and reacts in real time. Fullscreen it on a projector for parties, DJ sets, or band shows. No file, no upload, just sound in and visuals out.
Auto-cycle rotates presets on a timer, or you switch them manually like a VJ.
Free to run, free to export at 720p
The visualizer itself is free: full preset library, projector mode, mic input, no account required to start. A free account exports the video at 720p with a small watermark. A clean video is $4.99 on its own, up to 1080p and 10 minutes. Pro makes 8 exports a month, up to 1080p and 15 minutes each, for $14.99 a month or $144 a year. Unlimited makes every export you want, up to 4K, for $29.99 a month or $240 a year. Paid videos carry no watermark.
If all you want is a player, Butterchurn is genuinely great and costs nothing. The moment you want to publish what you’re seeing, that’s what Groovalizer is for.