The Jitter MACRO (aka MOD) was designed to improve the firing capabilities by exploiting a glitch in the game, triggered by rapidly alternating between two weapon states in rapid succession.

The MOD worked by modifying the input signals from the controller in such a way that the game received two separate button presses for every single physical button press on the controller, making it believe that the player was firing two different weapons, when in reality they are just rapidly alternating a pattern of two button states, which would vary depending on the specific Jitter MOD being used, but the principle was always the same.

By doing this, the Jitter MOD could greatly increase the rate of fire, making it a popular choice for COD players.

The Jitter MOD originally became popular with Black Ops 2 and continued to dominate Black Ops 3 until it was finally patched not long after Black Ops 4 was released.