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Vertical synchronization, more commonly known as v-sync, is when the frame rate is synchronized to match the vertical refresh rate of the screen. This means the double buffer is copied to screen's buffer in a small period between frames known as the vertical blanking interval. By updating the screen's buffer between frames, you ensure that only full frames are shown at a time.

To aid in synchronizing, virtually all video cards since the first home computers have the capability to enable an interrupt at the beginning of each vertical blanking interval (known as VBLANK).