Question 1

What is keystroke-to-screen latency?

Accepted Answer

It is the total delay from the moment a switch closes to the moment the resulting pixel change appears on your monitor. The chain has many links: switch debounce (1 to 8 ms), keyboard scan and USB poll (1 to 8 ms at 1000 Hz), OS input processing, browser event loop, the app's render and frame composition, GPU presentation, and finally monitor scanout and pixel response. Total budget on a fast gaming setup is 20 to 40 ms; on a typical laptop 60 to 120 ms is common.

Question 2

How does the browser-based latency test work?

Accepted Answer

DeviceCheckOnline shows a visual cue and measures the interval between that cue painting and your keydown event arriving. Because the browser only sees the keystroke after the OS, USB stack and switch debounce have already done their work, the reaction number includes your human response time plus the full input chain. To isolate hardware latency you need a high-speed camera or a probe like NVIDIA LDAT. This test still captures large differences between setups and is useful for comparing peripherals or measuring your own reflexes.

Question 3

What is a good reaction-to-screen number?

Accepted Answer

A typical human visual reaction time is 200 to 270 ms; trained gamers and athletes land around 150 to 200 ms. On top of your biology, your hardware adds 10 to 80 ms of input chain delay. So a great combined result on this test is roughly 180 to 220 ms, an average result 230 to 280 ms, and anything above 320 ms suggests either a low monitor refresh, a wireless or Bluetooth keyboard with high poll latency, a heavily loaded CPU, or browser throttling because the tab is backgrounded.

Question 4

How do I lower my input latency?

Accepted Answer

Plug the keyboard directly into a rear USB port (avoid hubs and KVMs). Use a wired or 2.4 GHz dongle rather than Bluetooth. Set the keyboard's polling rate to 1000 Hz if supported. On the display, raise the refresh rate and disable image-processing modes — many monitors have a true Game Mode that bypasses the processing pipeline. In games, cap FPS just below your refresh and enable NVIDIA Reflex or AMD Anti-Lag. Browser-side, close other tabs and ensure hardware acceleration is on.

Question 5

Why does my wireless keyboard feel slower than my wired one?

Accepted Answer

Most wireless keyboards run at 125 Hz polling (8 ms between reports) versus 1000 Hz (1 ms) for premium wired and gaming wireless. Bluetooth adds additional encoding and pairing-stack latency, often 15 to 30 ms on top of the radio interval. Modern gaming wireless using proprietary 2.4 GHz dongles (Logitech Lightspeed, Razer HyperSpeed) closes most of the gap and tests within a few milliseconds of wired. If your daily driver is Bluetooth, swapping to a dongle is the single biggest improvement available.

Question 6

Does monitor refresh rate matter for this test?

Accepted Answer

Yes — significantly. The browser can only paint at integer multiples of your monitor's refresh interval. At 60 Hz that interval is 16.67 ms, so even an instant keystroke can take up to one full frame to appear, averaging 8 ms of pure display latency on top of everything else. At 240 Hz the interval drops to 4.17 ms. If you are benchmarking peripherals, lock everything except the variable you are testing, and run /keyboard/repeat to verify OS key handling is consistent between runs.

Key latency.