Screen tearing is a visual artifact in video display where a display device shows information from multiple frames in a single screen draw.

The artifact occurs when the video feed to the device is not in sync with the display's refresh rate. This can be due to non-matching refresh rates—in which case the tear line moves as the phase difference changes (with speed proportional to difference of frame rates). It can also occur simply from lack of sync between two equal frame rates, in which case the tear line is at a fixed location that corresponds to the phase difference. During video motion, screen tearing creates a torn look as edges of objects (such as a wall or a tree) fail to line up. An example is in games that run in 3DFX SLI mode because of the way 3DFX SLI works, if one graphics card draws a frame faster than the other one, and it can be especially severe on a 3DFX Voodoo 5 6000 card because it has onboard quad SLI so the first GPU draws a frame in xxx time but the second one draws it x% faster, the third one y% slower and the fourth one z% faster.