A snubber capacitor is a capacitor connected to a high-current switching node. It’s designed to protect electronics from voltage spikes and transients that can occur during switching.
It’s common for the actions of a switch (i.e., opening or closing) to induce a high voltage across a device. Those voltage spikes cause failures if they exceed component ratings. Snubber capacitors offer an alternate path for excess energy to be absorbed and dissipated, ultimately reducing voltage spikes and ringing effects. Implementing snubber capacitors improves efficiency, reduces EMI and protects components.