Input Lag Test

What this test measures

Five times in a row, the field waits between one and three seconds and then turns white. You press Space or the React button as quickly as you can, and the page keeps the time between the change and your press. The result is the middle value of the five.

That number is not your display's input lag. It contains your own reaction time, which for most people is around 200 to 300 milliseconds and is by far the largest part, plus the keyboard or touchscreen, the browser, the operating system and the display. The test cannot separate them.

1. 1

   Rest your finger on the key before each trial and watch the field, not the buttons.

2. 2

   Do not guess the timing. Pressing before the field changes restarts that trial.

3. 3

   Run it a few times and compare setups: a wired keyboard against a wireless one, or one display against another on the same computer.

Keeping the numbers fair

Use the same finger, the same key and the same posture in every run, and take the median rather than your best single try. A tired or distracted person can be a hundred milliseconds slower, which is larger than the difference between most displays.

Comparing, not measuring

Because your reaction time is in every result, the useful part is the difference between runs, not the number itself. If the same person, on the same day, gets a much higher result on one setup than another, something in that chain is slower. Real input-lag figures come from equipment that photographs a screen and a button at thousands of frames a second.

For frame rate, use the Refresh Rate Test; for how motion looks, the Motion Blur / UFO Test.