vsync
also: vertical sync, vertical synchronization, frame sync
Vertical sync is a display synchronization technique that coordinates GPU rendering with the monitor's refresh rate to prevent visual tearing and improve frame pacing.
Vsync synchronizes the output of graphics frames with your monitor's vertical blanking interval—the moment when the display refreshes from bottom to top. Without vsync, the GPU may send a new frame mid-refresh, causing the screen to display parts of two different frames simultaneously, creating a visible horizontal tear.
When enabled, vsync caps the frame rate to match your monitor's refresh rate (typically 60 Hz). For example, on a 60 Hz monitor, vsync limits output to 60 fps maximum. This prevents tearing but can introduce input lag since the GPU waits for the monitor's sync signal before presenting frames.
Vsync is controlled through your graphics driver settings or game engine. Modern alternatives like adaptive sync (FreeSync, G-Sync) allow variable refresh rates, reducing tearing without the latency penalty of traditional vsync.