iCab is a web browser for Mac OS by Alexander Clauss, derived from Crystal Atari Browser (CAB) for Atari TOS compatible computers. It was one of the few browsers still updated for the classic Mac OS prior to that version being discontinued after version 3.0.5; today Classilla is the only browser still maintained for that OS.The downloadable product is fully functional, but is nagware—periodically displaying a dialog box asking the user to register the product, and upgrade to the "Pro" version.