V-Sync (vertical synchronisation) is a graphics setting that locks your game's frame rate to match your monitor's refresh rate. Without it, your graphics card sends frames to your screen at its own pace, which can cause visible horizontal tears across the image when the card and monitor fall out of sync.
When you enable V-Sync, the graphics card waits for the monitor to finish drawing one complete frame (at the vertical blanking interval) before sending the next one. This eliminates tearing but introduces a trade-off: if your frame rate drops below your monitor's refresh rate, you may experience stuttering or reduced responsiveness.
A practical example: you're playing a fast-paced shooter on a 60 Hz monitor. Without V-Sync, your GPU might output 80 frames per second, but your screen can only display 60. The mismatch causes torn frames. V-Sync caps output at 60 fps, so every frame aligns perfectly with the display cycle.
Modern alternatives like G-Sync (Nvidia) and FreeSync (AMD) offer a more flexible approach. They allow your monitor's refresh rate to vary dynamically with your GPU's output, eliminating both tearing and stuttering without the input lag penalty of traditional V-Sync.
When buying a gaming monitor or graphics card, check whether V-Sync is important to you. Competitive gamers often disable it to prioritise lower input latency, whilst those playing slower-paced games may prefer the visual stability it provides. High refresh rate monitors (144 Hz and above) make V-Sync limitations less noticeable.