- Your measured reaction time is human reaction plus hardware and software delay.
- Typical gaming systems add roughly 15 to 50 ms of system latency, and browser tests add some more.
- Display input lag is only one part of that chain, alongside the mouse, operating system, GPU and panel response.
- Comparing scores is only fair on the same equipment.
When TapReflex shows 250 ms, that number is not all biology. The signal has to travel through your computer to the screen, and your click has to travel back through the mouse and the browser. This guide separates the two parts so you can interpret your results.
What input lag means
Display input lag is the delay between a graphics card sending a frame and that frame appearing on the panel. It is separate from pixel response time, which is how fast pixels change color once they start, and from refresh rate, which sets how often the screen updates. Most gaming monitors have little processing delay, while TVs can add tens of milliseconds unless game mode is on. For a deeper look at the refresh-rate part, see our refresh rate guide.
The full latency chain
The table shows an illustrative budget for a typical gaming PC. Real values vary widely, so treat the numbers as ranges, not measurements of your system.
| Stage | Typical delay |
|---|---|
| Mouse sensor and USB polling | 1 to 4 ms |
| Operating system and browser event handling | 2 to 10 ms |
| Rendering and GPU queue | 5 to 20 ms |
| Display scan-out (refresh wait) | 2 to 8 ms |
| Pixel response and display processing | 1 to 10 ms |
| Total system latency | about 15 to 50 ms |
If your measured score is 250 ms and system latency is 35 ms, your underlying human reaction is closer to 215 ms. This is why two people can have the same reflexes but different scores.
How input lag is measured
Professional reviewers use hardware. A common method is to connect a photodiode or light sensor to a timer that is triggered by a mouse click, then measure the time until the screen changes. Other methods use a high-speed camera filming both the mouse button and the screen, and tools such as NVIDIA LDAT measure click-to-photon latency directly. These approaches avoid depending on software timing, which is why they are more accurate than any web page, including ours.
Why browser tests add delay
A browser adds event queuing, compositing and sometimes extra buffering before a color change reaches the screen. Using performance.now() and reading input on pointerdown removes the avoidable parts, but a few milliseconds remain, along with the display and mouse delay above. That is why browser results typically run 20 to 60 ms slower than laboratory measurements.
How to reduce each link
- Turn on game mode on any TV or monitor with processing options.
- Use the highest refresh rate your screen supports, set in the operating system.
- Use a wired mouse with 500 to 1000 Hz polling.
- Close background apps and extra browser tabs.
- Use VRR or a frame cap rather than traditional V-Sync.
Using this knowledge
Do not compare your score with someone else's unless the hardware is similar. Instead, measure yourself over time on the same setup with the reaction time test, and judge progress by your own average. Changes to hardware show up as a step change, while training and sleep show up as a slow drift.