Except you can pick and choose. If all you want is the dom-util-event stuff, it's 36KB unminified. That's the core, and it gets you more features and a more san

Except you can pick and choose. If all you want is the dom-util-event stuff, it's 36KB unminified. That's the core, and it gets you more features and a more sane API than the 32KB unminified prototype.js. Of course, adding animation on adds weight in both libraries. Tacking on scriptaculous core + effects tacks on an additional 44kb. Tacking on YUI's animation and effects package tacks on 48KB of more featureful and sane API. If you want the entire (slow, buggy, and not very cross-platform) scriptaculous library loaded, prepare to load up 156KB. tl;dr: unminified, YUI-dom-event + animation is 84KB unminified. Prototype + Scriptaculous is 76KB unminified. YUI is faster, has a more sane API, more features, doesn't pollute the global namespace, and doesn't insanely swallow and mute errors. Oh, yeah, and it has better API documentation.... (sidenote: YUI framework is 10mb without docs, but that includes: minified, unminified, unit tests, and a metric shit-ton [technical term] of plugins. Of course, if you're going with prototype or jQuery, you've got to scour the 'net looking for plugins that do the same thing. They come packaged with YUI.)