What is VSync and should you enable it?

• VSync synchronizes display and GPU frame rates to prevent screen tearing and stuttering.

• VSync reduces FPS by limiting GPU output to match the screen refresh rate.

• Adaptive VSync adjusts timing based on GPU performance to reduce input latency.

Video games usually have an option in their graphics settings called “VSync”, but what does VSync do and should you enable it? I’ll explore the pros and cons of VSync technology to help you decide when it’s the best option.

What is VSync?

VSync (abbreviation for vertical sync) is a technology used in displays and graphics cards to synchronize the screen refresh rate with the graphics card’s frame rate. This ensures that each video frame is displayed on the screen at the right time without screen tearing or stuttering.

When the refresh rate and frame rate are out of sync, the screen may display part of one image and part of another image simultaneously, resulting in a torn image. This can happen when the frame rate is higher than the frame rate, causing the screen to display multiple frames at once, or when the refresh rate is higher than the frame rate, causing causes the screen to skip frames.

For demonstration, here is a video clip that I took from the upper left corner of my screen, while playing Eternal destiny with Vsync completely disabled. The video was filmed using my iPhone’s slow motion feature, so you can clearly see the screen tear lines.

A GPU has several memory “buffers” that store and process graphics data. The “front” and “back” stamps are two such stamps used in a “double stamp” technique.

The front buffer is the part of GPU memory visible on screen. It contains the image data currently displayed on the screen. When the GPU renders a new frame, it stores the data in the back buffer, which is not visible on the screen.

Screen tearing occurs when the buffer is “knocked over” midway through a screen refresh cycle. With VSync enabled, the GPU waits for the next screen refresh to start before sending the contents of the back buffer to the screen.

Does VSync reduce FPS?

You should know that VSync reduces frame rates, and this happens in several ways. The main method is how vertical sync prevents your GPU from rendering more frames than the screen refresh rate. In other words, a 60 Hz monitor will not receive more than 60 frames per second.

Additionally, double-buffered VSync has a serious drawback. If the device connected to the display cannot produce frames at a sufficient rate, the current frame will persist for two refreshes, dropping the FPS to half the refresh rate.

Triple buffering is a similar technique but with an additional buffer. This third buffer is used to store an intermediate frame that is rendered by the GPU, while the front buffer is displayed on the screen and the back buffer waits for the next frame.

The most recent frame ready to be switched to the front buffer at the start of display refresh is sent there. This reduces the extent of frame rate reduction when your GPU can’t always keep up with the screen refresh rate, because there is almost always a new frame available. However, triple buffering slightly increases latency and is therefore not appreciated by fans of online multiplayer.

“Adaptive” VSync attempts to address the drawbacks of these VSync methods by adapting the timing between refresh rate and frame rate based on the performance of the graphics card. When the frame rate is higher than the refresh rate, Adaptive VSync behaves as if VSync is enabled and synchronizes the refresh rate with the frame rate to prevent tearing and stuttering.

However, when the frame rate is lower than the refresh rate, Adaptive VSync behaves as if VSync is disabled and allows the graphics card to render and display frames as quickly as possible without any limitations. This can improve frame rate and reduce input latency without causing tearing or stuttering.

VSync displays and variable refresh rate

In addition to the VSync technologies we’ve talked about so far, variable refresh rate (VRR) technologies can also play a role in improving your gaming experience. If you have a VRR display that uses HDMI VRR, AMD FreeSync or NVIDIA G-Sync, it can dynamically change its refresh rate to match the GPU’s frame rate.

This solves virtually all of the problems other forms of VSync have in terms of input latency or frame rate reduction. However, if your GPU can output more frames than the display’s maximum frame rate, you may still want to enable VSync in conjunction with VRR technology.

If your frame rate drops below the minimum refresh rate of your VRR-enabled display, you will still need an LFC (Low Frame Compensation) feature. Not all VRR displays include this feature, so be careful when making a purchase.

When should you enable VSync?

When to enable VSync depends on your personal preference. Vertical sync can provide a smooth and immersive experience, but it can also have some drawbacks. Disabling VSync can improve frame rate and responsiveness, but it can also cause visual artifacts like tearing. Whether you can live with the apparent level of tearing is a personal decision, and it’s pretty easy to try each game with this feature turned on and off.

Some gamers may prefer to disable VSync when playing games that require precise timing and coordination, such as first-person shooters, real-time strategy games, or esports games.

In single-player games that don’t rely on low levels of input latency, it’s usually best to enable VSync. However, we do not recommend using double-buffered VSync unless there is no other option available. Triple-buffered VSync is a better option, with Adaptive VSync being an even better option if possible. Most modern games have at least triple-buffered VSync, even if it’s not labeled as such.

With new technologies like VRR, Adaptive Sync, and more refined versions of VSync, the drawbacks of traditional VSync have all but disappeared. So if you have access to these new toys, don’t hesitate to use them!