When you apply a mask to an object, Premiere Pro can let the mask automatically follow the object as it moves from one frame to another. For example, after blurring a face using a shape mask, Premiere Pro can automatically track the movements of the masked face from frame to frame as the person moves.
When a mask is selected, the Effect Controls panel displays controls for tracking the mask forward or backward. You can choose to track the mask either one frame at a time or until the end of the sequence.
Click the wrench icon
to modify how masks are tracked. You can select from a few choices to provide the most effective tracking: