Header bidding and waterfall are two different ways of selling ad spaces to advertisers. Both of these methods are different and had an effective The waterfall method, or daisy chaining, was the method of old when modern algorithms were unavailable. Here, the publisher sets the priority for each advertiser or ad network and also sets a price floor, i.e. minimum accepted price for ad space. When an advertiser meets the price floor, the inventory is sold to them.
Header bidding is the most accurate form of the auction and has almost replaced the waterfall model. Here, multiple demand partners can bid for inventory simultaneously. The highest bidding wins, allowing publishers to earn maximum revenue every time. Hence, header bidding has replaced the waterfall model entirely as it allows publishers to make more money in less time.