In the context of internet speed testing, jitter refers to variations in the delay or latency of data packets as they travel from your device to a remote server. It denotes instability or fluctuations in packet delivery time. Jitter is commonly measured in milliseconds (ms) and is a measure of the inequalities between individual data packet travel times. A higher jitter number implies that packet delivery times vary more, whereas a lower value suggests a more consistent and dependable delivery.