G-Sync is a proprietary variable refresh rate (VRR) technology developed by Nvidia. It allows a compatible monitor to change its refresh rate on the fly to match the frame rate your graphics card is producing, rather than forcing your card to match a fixed monitor refresh rate.
Traditionally, monitors refresh at a set frequency: 60Hz, 144Hz, or 240Hz, for example. If your graphics card outputs 110 frames per second on a 144Hz monitor, the frames don't align perfectly with the monitor's refresh cycles. This mismatch causes screen tearing, where you see portions of multiple frames on screen at once. G-Sync eliminates this by letting the monitor wait for each new frame before refreshing, keeping the image locked to your card's output.
G-Sync monitors use special hardware (a module inside the display) licensed from Nvidia. This adds to the cost compared to standard monitors. You'll need an Nvidia GeForce GPU (typically GTX 650 or newer) to use it.
Real-world example: Playing a fast-paced shooter where your RTX 4070 outputs 85 fps. A G-Sync monitor smoothly adjusts from its normal 144Hz down to 85Hz for those moments, keeping gameplay fluid. Without G-Sync, you'd see tearing or stuttering as frames fight the monitor's refresh cycle.
When shopping, check that your monitor bears the G-Sync badge and supports the refresh rate you need. Higher-end gaming monitors commonly feature it. Note that AMD graphics cards use FreeSync (a similar but open standard) instead, so confirm your GPU brand matches the monitor technology. Gamers focused on competitive shooters and high-refresh gaming gain the most benefit.