Input lag test
Click (or tap, or press Space) the moment the panel turns pink. Ten rounds give you a median click-to-screen time for your whole setup. Change one setting, run it again, and compare.
- Median
- – ms
- Best
- – ms
- Spread
- – ms
What this number includes
A browser can timestamp your click, but it cannot see the moment light leaves the panel. So this measures the whole loop: the page asks for pink on the next frame, the display shows it, you see it and click. Human reaction dominates (usually 180–280 ms). Because that part stays roughly constant for the same person, differences between runs point at your setup. A difference of 30 ms or more between Game Mode on and off is real; 5 ms is noise.
To measure a monitor's own lag, reviewers use a photodiode on the screen and a device that injects clicks, like NVIDIA's LDAT or a Leo Bodnar lag tester. That is the only way to isolate the display.
Measure display lag with a slow-motion camera
To get closer to the display's own lag without lab gear, film the screen and your mouse together in slow motion:
- Set your phone to its highest slow-motion frame rate (often 240 fps). Each recorded frame is then about 4.2 ms.
- Frame the mouse button and the pad above in one shot. Start a round and click when it turns pink, then click once more to start the next round, filming the moment your finger presses.
- Step through the video frame by frame. Count frames from the button visibly bottoming out to the pad changing colour on the next round's start.
- Delay in ms = frames counted ÷ camera fps × 1000. Repeat 5–10 times and take the median.
This still includes the mouse, PC and browser, but not your reaction time, so it's good for comparing Game Mode on and off, or two displays on the same PC.
Where the milliseconds go
Adjust each stage of the chain to see which ones matter. Typical values for a 144 Hz gaming setup are pre-filled.
System latency (everything but you): 25 ms. Total with reaction: 225 ms. Refresh rate matters twice here: it sets the average wait for the next refresh (half a frame) and caps how fast frames arrive.
Questions people ask
Does this measure my monitor's input lag?
Not in isolation. It measures your whole chain: mouse or touch, operating system, browser, display refresh, the monitor's processing, and your own reaction time. Browsers cannot see when light leaves the panel. It is useful for comparing settings (Game Mode on vs off, 60 vs 144 Hz) on the same setup, not for comparing against a monitor review.
What is a good input lag for gaming?
Reviewers who measure with photodiode rigs typically class monitor processing lag under about 10 ms as excellent for competitive play. TVs outside Game Mode can add 50 ms or more.
How do I reduce input lag?
Use Game Mode on TVs, run the highest refresh rate, turn off motion smoothing and heavy post-processing, use a wired mouse, and in games cap FPS slightly below refresh with VRR on, or turn off VSync if tearing doesn't bother you.
Why do my results vary so much?
Most of the variation is human reaction time, which differs by tens of milliseconds between tries. That is why the test averages many rounds and shows the spread. Compare medians, not single tries.