This article describes the Unit Type (StarCraft) or Attributes (StarCraft II). For information on the device, see here.
A detector is a unit or structure with the ability of detection, meaning it is able to reveal cloaked and burrowed enemy units, or hallucinations. Having enough detectors across the map is an important aspect of any player's strategy, as they will provide forewarning on potentially fatal attacks from otherwise unstoppable hidden units.
While every race and faction has a mobile detector unit, they also have a passive stationary defense building that provides detection, such as photon cannons, missile turrets, and spore colonies. Detector buildings lack the mobility of units, but make up for it by being much more durable and by being equipped with more powerful weapon systems. Regardless of which race a player uses, if the opponent uses cloaked or burrowed units, having a detector in your army before engaging your opponent is pivotal.
Detectors can be stationary (buildings) or mobile (units). Once a detector uncovers a cloaked unit, any friendly unit can fire on it. This capability is especially critical when faced with a ghost targeting a nuclear missile or an arbiter providing cover for a number of units. Detector units trapped in Lockdown or hit by Optical Flares will lose their ability to detect.
Ensnare, Maelstrom, Plague, and Stasis field will reveal cloaked protoss and terran units caught in their areas of effect for the ability's duration. Burrowed zerg units are unaffected by these abilities while burrowed, but if hit by these abilities while above ground, they will be revealed if they burrow. The Devourer's Acid Spores, as well as Lockdown and Parasite, will reveal cloaked (and in the case of Parasite, burrowed) units that are affected, but these units must already be detected in order to be targeted by the ability.
Irradiate reveals any cloaked and burrowed units it directly affects, and will damage cloaked units adjacent to the target without revealing them, but will not damage burrowed units adjacent to the target. EMP shockwave will not affect protoss cloaked units or zerg burrowed units, but terran ghosts and wraiths will be affected and lose all their energy, causing them to immediately decloak.
Unusually, Defensive Matrix will reveal the friendly unit that is affected by it, to enemy units. The same applies to friendly units that are caught in the area of effect of Plague, and then burrow while still affected.
An infestor launches a projectile with a speed of 15; enemy units within the area of effect (2.25 radius) have their speed reduced by 75% and suffer 30 damage over 3 seconds. Cloaked and burrowed units are revealed.
Fungal Growth stops the use of Blink, Tactical Jump and prevents units from burrowing or unburrowing. Affected units can not be loaded into buildings or transports.