script.aculo.us targets the same browsers as the Prototype Java Script framework:

• Microsoft Internet Explorer for Windows, version 6.0 and higher
• Mozilla Firefox 1.0/Mozilla 1.7 and higher
• Apple Safari 1.2 and higher

Other browsers which are reported to be compatible are:

• Konqueror
• Camino
• Opera 7.54, but no AJAX and no opacity-based effects. Dragging may cause text to be selected
• Opera 8, but no opacity-based effects (opera 9 support opacity).