The combadge was a small, multi-purpose communications and universal translation device, which usually took the form of an organization's insignia designed to be worn by the user.

The Starfleet combadge was a crystalline composite of gold, microfilament, silicon, beryllium, and carbon-70. They were designed for on-board ship communication with other Starfleet personnel when using the internal communication system was impossible or impractical, for accessing the on-board computer when not in an area that the computer is monitoring, for ship-to-shore communications, and for direct communication to another combadge. Combadges also were configured to act as universal translators, often translating in real time.

Combadges were activated by pressing it once and calling out the name or general area of the intended recipient. They could then be deactivated by another single press. Multiple presses on the badge could be used as an attempt to gain the attention of a ship's crew. Due to the size of the combadge, its working range was limited to five hundred kilometers, although a starship could boost the signal to bridge larger distances.

Combadges could be used by the transporter as a way to lock on to Starfleet personnel; more generally, the transporter could lock onto any person or object with a combadge attached or nearby, thus making transport faster and more accurate.