What is the difference between an auto dialer and a predictive dialer?

An auto dialer works through a contact list and dials numbers one at a time, connecting answered calls to an available agent. A predictive dialer goes a step further by using algorithms to dial multiple numbers at once and predict when an agent will become free, so the next live call is ready the moment one conversation ends. Predictive dialers work best for large outbound call centres where volume and speed are the priority.