Channel Definition Format (CDF) was an XML file format formerly used in conjunction with Microsoft's Active Channel, Active Desktop and Smart Offline Favorites technologies. The format was designed to "offer frequently updated collections of information, or channels, from any web server for automatic delivery to compatible receiver programs."[1] Active Channel allowed users to subscribe to channels and have scheduled updates delivered to their desktop. Smart Offline Favorites, like channels, enabled users to view webpages from the cache.