A predictive dialer dials a list of telephone numbers and connects answered dials to people making calls, often referred to as agents. Predictive dialers use statistical algorithms to minimize the time that agents spend waiting between conversations, while minimizing the occurrence of someone answering when no agent is available.

When dialing numbers one at a time, there are two sources of delay. First, only some fraction of dials are answered; for example, if 1 out of 3 dials are answered, a predictive dialer might dial 3 lines every time an agent becomes available. Second, even dials that are answered take some time before being picked up. If it typically takes 10 seconds for someone to pick up, and conversations typically last 90 seconds, a predictive dialer might start dialing at 80 seconds. A predictive dialer does so by discarding all tones and only passing "Hellos" from the lead to the agent.

Dialing one number at a time, only when an agent is available, typically keeps agents utilized for 40 minutes per hour (33% idle time). Predictive dialing can increase utilization to 57 minutes per hour (5% idle time).

Predictive dialers may be standalone hardware devices, cloud-based, or they may be integrated in software with call center or contact center platforms. A cloud-based predictive dialer provides the functionalities of a traditional predictive dialer without requiring installation on the local device and reduces the dependency on the hardware. The dialer can often also perform less aggressive dialing modes such as, power, progressive, or preview dialing.