Is it safe to run a microwave empty?

No, it is not safe to run a microwave empty. When a microwave operates without food or liquid to absorb the energy, the microwaves can reflect off the walls and potentially damage the magnetron, the component that generates the microwaves. This can lead to overheating and may cause the microwave to malfunction or even break down. Always ensure there's something inside, even if it's just a cup of water, when using the microwave.