Vsync or vertical synchronisation is a technology for matching the refresh rate of a gaming monitor and the FPS (frames per second) of a game. This technology helps to reduce screen tearing, which is dreaded in the gaming community.
FPS refers to the rate, at which a GPU sends pixel information to the monitor. If the refresh rate is slower than the FPS, multiple frames crash together, which causes screen tearing. The refresh rate of a monitor is the rate at which the monitor takes these pixel input values.
Suppose that you have a monitor with a refresh rate of 60 Hz and the and the graphics card is sending a rate of, say, 100 FPS to the monitor. In this case, there is a mismatch between the two and screen tearing takes place. What Vsync does is that it matches both these things. This gives a better gaming experience as both the image input and output are in complete synchronisation.
Advantages and disadvantages of Vsync
The most significant advantage that Vsync provides is that it reduces screen tearing. Also, Vsync can be used on older monitors that do not have Freesync or Adaptive sync. Vsync is not proprietory like Freesync and Adaptivesync and works on any combination of GPUs and monitors. To synchronise the FPS and refresh rates when the former is higher, the GPU reduces the FPS to match the refresh rate of the monitor. This happens in most of the old games that are available. When the FPS drops below the refresh rate, the monitor’s refresh rate is also reduced, which causes input lag. Also, in this case, the graphics card gets heated due to rendering at a more output rate.
Triple buffering is another option that helps to reduce issues caused by Vsync, but it has a memory overhead as the GPU has to use its memory to save an extra frame.
Also read: 60Hz vs 120Hz vs 144Hz vs 240Hz displays
When should you turn it on or off?
If you have a monitor that is old and does not support advanced features like Adaptivesync and Freesync. You can use Vsync to reduce screen tearing. Also, if the FPS is below or equal to the monitor’s refresh rate, then there is no need to turn on the Vsync.
But if Freesync or Adaptivesync is available, you should go for it. It fixes issues of Vsync by switching it on and off automatically when the FPS drops below the refresh rate.
Also read: What is Ambient Occlusion in gaming?