Variable refresh rate (vrr, adaptive sync, freesync, g-sync) works by dynamically matching the refresh rate of a display to the active framerate. However, VRR needs some configuration to fully work: mainly V-Sync and an FPS limiter.

V-Sync: With VRR on + V-sync off, if a new frame becomes ready early while the previous frame is still being scanned out onto the display (from top to bottom), the remaining scanout will be replaced by the new frame, resulting in tearing. The same is true for a frametime spike where the old frame keeps being displayed until a new one is ready. When V-Sync is enabled in conjunction with VRR, the driver will adhere to the display scanout by holding the new frame until a new scanout, which ensures no tearing. This replaces default V-Sync buffered behavior and therefore the only added input lag is preventing the frame from being overwritten during the current scanout.

FPS Limiter: VRR only works inside a display’s refresh rate range and is automatically disabled when the framerate exceeds the max refresh rate. Capping at the display’s max refresh rate is insufficient as FPS limiters aren’t exact and can slightly overshoot the cap due to frametime variances, causing VRR to rapidly disengage/re-engage, which can also cause flicker. Furthermore, V-Sync will fall back to regular buffered behavior when VRR turns off, increasing input lag. A common rule of thumb is to have a framerate cap at least 3 below the max refresh rate.

Nvidia GPUs:

• G-Sync + (Nvidia Control Panel) V-Sync On + FPS limiter is the ideal configuration for no screen tearing with no extra buffering.
• Reflex (on / on + boost) is the best FPS limiter approach when supported by a game, but other options include in-game fps limiter, NVCP Low Latency Mode “Ultra” or RTSS (preferably Reflex mode).

Nvidia - A Guide To Better System Latency:

However, if you have a variable refresh rate display, like an NVIDIA G-SYNC monitor, you can get the best of both worlds: no tearing (if your FPS is below your refresh rate), and no VSYNC latency.

For G-SYNC gamers who don’t want to tear, keeping VSYNC ON while using NVIDIA Reflex or NVIDIA Ultra Low Latency Mode, will automatically cap the framerate below the refresh rate, preventing VSYNC backpressure, eliminating tearing, and keeping latency low if you become GPU bound below the refresh rate of your display. Do note, however, that this method will result in slightly higher latency than just letting your FPS run uncapped with NVIDIA Reflex enabled.

• Note that the last point only applies to scenarios with uncapped FPS exceeding the expected cap with minimal render queue size (Reflex on or sub-99% GPU usage).

AMD GPUs:

• Freesync + (in-game) V-Sync On + FPS limiter is the ideal configuration for no screen tearing with no extra buffering.
• Contrary to Nvidia Reflex it appears driver-side limiters on Radeon can add noticeable¹ latency, at least in some games. Therefore an in-game limiter is preferred for input lag.

Note that in-game limiters often don’t apply to menus where framerate isn’t necessarily capped, which can cause flicker as mentioned previously.

Testing

Blur Busters - G-SYNC 101

• 1000 FPS high speed camera @ 240 Hz in Overwatch
• NVCP V-Sync + G-Sync + in-game FPS limiter at least 3 below max refresh rate ideal VRR config (testing predates Reflex)

Techless - You are using G-sync wrong (probably)

• LDAT, left of screen center @ 240 Hz in Overwatch 2 & Valorant, 7900X + 4080
• NVCP V-Sync + G-Sync + Reflex ideal VRR config

FR33THY - NVIDIA Does It Add Input Lag?

• Custom click-to-photon latency tester @ 240 Hz in Valorant, 5800X3D + 3090
• NVCP V-Sync + G-Sync + Reflex (or LLM Ultra) ideal VRR config

FR33THY - AMD Does It Add Input Lag?

• Custom click-to-photon latency tester @ 240 Hz in Valorant, 5800X3D + 7900XT
• Radeon Software V-Sync On + In-Game V-Sync On + Freesync + in-game FPS limiter ideal VRR config
• Only tested cap 15 fps below max refresh rate, but 3 should work the same.
• At least in Valorant, external (Radeon Software, RTSS) framerate limiter adds far more input lag than in-game compared to behavior on GeForce

Battle(non)sense - G-Sync & Reflex Low Latency - How To Use Both

Battle(non)sense - Get The Most Out Of Your G-Sync Monitor

Battle(non)sense - NVIDIA G-Sync + Null Setup & Input Lag Results

Battle(non)sense - FreeSync vs. G-Sync Delay Analysis

• 1200 FPS high speed camera