A specialized hardware device or software in a desktop or laptop computer that captures packets transmitted in a network for routine inspection and problem detection. Also called a "sniffer," "packet sniffer," "packet analyzer," "traffic analyzer" and "protocol analyzer," the network analyzer plugs into a port on a network hub or switch and decodes one or more protocols into a human-readable format for the network administrator. It can also store packets on disk for further analysis later on.

Network analyzers can also analyze the packets in real time in order to alert the administrator about problems. Hardware network analyzers can detect voltage and cable problems, which software-only analyzers cannot. See port mirroring.