Input lag: what a browser can tell you
This flash-to-click task records your reaction plus system timing across 10 trials. It cannot isolate monitor input lag or measure click-to-photon latency. Use the results as a reaction exercise, not a display specification.
What is monitor input lag?
Input lag is the delay between a user action (mouse click, keystroke) and a visible change on the monitor. It combines signal processing in the display, monitor electronics, and the system render pipeline. Most gaming monitors target 1-5ms input lag; budget and TV panels can reach 20-100ms.
Input lag vs response time
These are often confused. Response time (GtG, MPRT) is how fast a pixel changes color — it affects ghosting. Input lag is how fast the monitor displays the signal it receives after processing it. A monitor can have fast GtG but high input lag due to extensive image processing.
Why this is not a hardware measurement
The timer begins around a browser animation callback, before the physical panel necessarily changes. Your response includes seeing the flash, deciding to click, mouse timing and browser scheduling. A lower score does not establish that one monitor has less input lag.
What to compare instead
For motion clarity, compare the same moving pattern at different overdrive settings. For input lag, consult measurements made with a documented camera or photodiode method at the same refresh rate and display mode. Check your display manual for a low-latency or game mode; cable type or HDR alone does not determine latency.
Read the full browser-test limitations.
Also try our Reaction Time Test and What Is Input Lag guide.
Testing guide
How to interpret this reaction check
The number shown is flash-to-click reaction timing. Human reaction, input handling and browser scheduling dominate this task; it does not isolate display latency.
Use these patterns as visual checks or browser estimates. Understand the limits or record your monitor checks.
Best for
- Trying a short visual reaction exercise.
- Learning the difference between reaction time and hardware latency.
How to run the test
- 1Use the same device and input method for each trial.
- 2Click or press the focused button when the flash appears.
- 3Record several trials; do not interpret the score as monitor input lag.
How to read the result
A lower number means a faster recorded reaction in that trial.
Practice, anticipation, fatigue and system load all influence the result.
A hardware input-lag measurement requires a different setup.
Related tools and guides
Frequently asked questions
Does this measure monitor input lag?
No. It times your response to a flash and includes human reaction. It cannot isolate monitor processing or click-to-photon delay.
Can I compare two monitors with this score?
Not reliably. Differences in reaction, browser scheduling and input timing can exceed the display delay you are trying to compare. Use a documented hardware measurement method.