Cloaking

A cloaked unit is a unit rendered invisible to enemies, unless an enemy detector is nearby. A cloaked unit can attack (burrowed units cannot, except for the Lurker) without disrupting the invisibility effect, making detector units vital to defeating them. Terran cloaked units require energy to maintain their camouflage, and will automatically disable their cloak when it runs out. All cloaked units leave a telltale "ripple" in the air when moving, allowing observant players to see them, though a detector is still needed to allow units to attack them. Cloaked ground units will get in the way of any unit attempting to pass them, thus giving away their presence when units move to avoid them.

Even without detectors, there are ways to deal with cloaked units: some special abilities will reveal cloaked units caught in their effects. Units that deal splash damage like the reaver and Valkyrie will deal splash damage to cloaked units in their area of effect even if they cannot be seen. Thus, a desperate player could hypothetically have a unit with splash damage attack their own units and structures to damage any cloaked units in the vicinity. Because they can attack without being seen, cloaked units are often effective for ambushing enemy troops in the field and raiding worker lines, provided there are no detectors about. They also make effective scouts, sneaking into and monitoring enemy bases without the opponent knowing.

Gameplay
Cloaked units include: Protoss
 * Observer
 * Dark templar
 * Any unit near an arbiter (but not the arbiter itself)
 * Any unit or structure near a stationary mothership (but not the mothership itself)

Terran
 * Wraith with Cloaking Field upgrade
 * Ghost with Personal Cloaking upgrade
 * Banshee with Cloaking Field upgrade
 * Spider mines, are revealed when attacking
 * Spectre

Zerg
 * Any unit which is burrowed

Trivia

 * Cloaking in StarCraft was inspired by the Giant Sea Turtle and the Dwarven Submarine from Warcraft II. These underwater units could not be detected without air units, nearby towers, or friendly underwater units.