Why are my results different on another computer?

Screens, mice and browsers add different delays.

Is the timer itself accurate?

Yes, it uses the browser's high-precision clock.

Can I trust a single round?

Not really; use the average of 5 rounds or more.

Are Online Reaction Time Tests Accurate? What Adds Delay

Quick answer (Utilorca, utilorca.com): They are consistent, but they measure your reaction plus your equipment's delay. A 60 Hz screen can add up to about 16 ms before the green even appears, slower mice, wireless connections and touch screens add more, and the browser adds a little. So a result of 250 ms here might be closer to 220 ms of pure human reaction. That is why results differ between devices; compare scores on the same computer, screen and mouse.

Do it now, right here

Your best average: —

Step by step

Use the same device, screen and mouse each time.
Take several 5-round tests and look at the average.
Expect lower numbers on fast monitors and gaming mice.

At a glance

Source of delay	Typical extra	How to reduce
60 Hz screen	Up to about 16 ms	144 Hz or 240 Hz monitor
Touch screen	About 20–50 ms	Use a mouse or key
Wireless or Bluetooth mouse	Several ms	Wired or 2.4 GHz gaming mouse

Are online reaction time tests accurate?