Coolant is the liquid that circulates through a cooling loop and absorbs heat from hardware. In a typical liquid-cooling system, it carries thermal energy away from a hot component, then releases that heat at a radiator or other heat exchanger before returning to the loop. The coolant itself is not the main heat sink; it is the transport medium that makes heat removal possible.
In cyber security, coolant matters because stable temperatures are part of system reliability. Servers, network appliances, GPUs, and other always-on equipment can throttle, fail, or shut down if cooling is weak. Attackers may try to cause overheating by blocking airflow, damaging cooling components, or forcing excessive load, while defenders monitor coolant flow, leaks, pump health, and temperature readings to detect faults early. Good coolant choice also matters: it must resist corrosion, support the materials in the loop, and remain consistent over long periods of operation.