What causes screen tearing and how to fix it?

Most gamers have experienced the dreaded screen tearing phenomenon. One moment you’re fighting enemies in a fantasy world, and the next moment you’re looking at a patchwork of jagged images. Your in-game avatar’s torso is separated from their legs and head, and the path in front of you is also torn apart.

This is called screen tearing, and is part of a set of visual artifacts that can disrupt your gaming session. While this is much more common with PC gaming, it can sometimes be a problem for console gamers as well. The good news is that we not only know exactly why screen tearing happens, but also how to fix it.

The problem is primarily caused by a mismatch between the speed at which your computer hardware renders video images and the speed at which your screen can display them to you. But thanks to a combination of technologies that help coordinate images between your graphics card and your monitor, screen tearing is no longer the scourge it once was.

The cause of screen tearing is quite simple: your GPU renders images at a different speed than your monitor displays them. Think of the image rendering pipeline as a two-person assembly line, where your GPU “transmits” video frames to your monitor. The problem is that many GPUs are not tied to monitor speed. Sometimes a GPU overtakes the monitor, rendering up to hundreds more frames per second than the monitor can display. Other times, your GPU may render very few frames if a game puts a heavy load on it.

Normally, a monitor must refresh on a set schedule, just as the person at the end of an assembly line must drop the last item handed to him before accepting a new one. The speed at which it can do this each second, measured in hertz, is called the refresh rate. GPU output is measured in frames per second (fps).

On basic monitors, refreshes occur 60 times per second. Gaming-focused monitors offer higher refresh rates, like 144Hz or higher – 240Hz is becoming more common among mid-range gamers and even 1000Hz monitors are now on the market. As refresh cycles become faster, they become more and more imperceptible to the untrained eye.

But you can easily see what happens when the GPU renders a new frame into the buffer before the monitor has analyzed the previous one. This can cause parts of both images to appear on your screen at the same time, as the monitor scans the frame buffer from top to bottom.

The incongruities between these images are the dreaded screen tearing effect, where, for example, the top of a tree appears next to its trunk. These slices occur because two video frames simultaneously occupy different horizontal strips of the screen.

The good news is that screen tearing is essentially a solved problem. With variable refresh rate technology, monitors can synchronize their refresh rates with the frame rate of a graphics card, eliminating the possibility of the monitor displaying two frames at once. The main names for VRR are NVIDIA G-Sync and AMD FreeSync.

None of these should be confused with V-Sync, another widely available technology designed to thwart the screen in video games. V-Sync forces the GPU to wait until the monitor is ready before transmitting a new frame, instead of shoveling new frames as fast as it can produce them. To reuse the assembly line analogy, V-Sync tells the person at the beginning of the line exactly when to hand off the items to the second worker.

But that in itself can cause problems. Since each frame now waits for its turn, V-Sync can cause input lag. And if the frame rate drops for a while, the monitor repeats the frames, causing stuttering, which is just as annoying as screen tearing. This doesn’t mean you should avoid using V-Sync, however.

G-Sync and FreeSync take a different, more efficient approach: variable refresh rates. With G-Sync, traditionally, a hardware module inside officially supported monitors coordinates with the GPU. It relates the monitor’s refresh rate to that of the GPU, waiting to draw the next frame until the GPU finishes it. Meanwhile, newer “G-Sync enabled” monitors can use this feature without dedicated hardware. (The next generation of G-Sync will also address motion blur through a feature called Pulsar.)

FreeSync achieves the same goal without a hardware module by using the VESA Adaptive-Sync protocol. In both cases, VRR is a bit like adding a foreman to the assembly line who ensures that the worker at the end of the line adjusts his pace based on what the worker at the front is doing.

You may have noticed that the VRR seems at odds with the exact problem it was designed to solve. If screen tearing is caused by out-of-sync between a monitor and the GPU, and VRR simply tells the monitor how fast the GPU is running at any given time, we still haven’t accounted for what happens when the GPU exceeds the monitor’s maximum refresh rate. And you are right; VRR cannot make a monitor faster than it already is. This only works well in that monitor’s native refresh window, outside of which visual tearing still occurs.

This is why it is recommended to use both V-Sync and G-Sync or FreeSync. While VRR helps keep frame rates in sync between the GPU and monitor, V-Sync ensures that the GPU’s frame rate output cannot exceed the monitor’s capabilities by keeping it within the VRR window. However, it’s best to enable V-Sync from your computer’s global NVIDIA or AMD graphics settings, rather than using the game’s settings, and to set the game’s frame rate limit slightly below your monitor’s maximum refresh rate. For example, gaming on a 240Hz monitor should be capped at around 235fps. In addition to preventing screen tearing, this will also help stabilize your frame rates for smoother gaming.