Vsync

Vsync, short for vertical synchronization, is a display option that coordinates a GPU's frame output with a monitor's refresh rate to reduce tearing. Tearing happens when frames are drawn at times that do not align with the screen's horizontal retrace, producing a disjoint image where parts of multiple frames are visible at once.

When enabled, vsync attempts to synchronize rendering to the vertical blanking interval. In classic implementations, the GPU uses double buffering and delays presenting a frame until the monitor is ready for a new refresh. If the GPU cannot sustain the target rate, frames may be delayed, dropped, or repeated, leading to stutter or perceived lag.

Benefits include tearing-free images and more stable vertical motion. Drawbacks can include increased input latency, reduced frame rates, and occasional stuttering when rendering time fluctuates. On some systems, enabling vsync can cause micro-stutters or jank during rapid camera movement.

Modern display technology offers adaptive synchronization alternatives, such as dynamic refresh rate technologies that couple the monitor refresh to the GPU's real-time frame time. These technologies (often branded as G-SYNC and FreeSync) aim to eliminate tearing while minimizing latency by adapting to varying frame rates. There are also software techniques like fast/low-latency sync that attempt to mitigate lag while maintaining smoothness.

Vsync remains a standard option in many graphics control panels and is widely supported across APIs and hardware. It is most beneficial on displays with fixed or stable refresh rates; on variable-rate displays or high-latency setups, adaptive sync or disabling vsync may yield better overall responsiveness.