ReactionCheckA small test with instant feedback.
Browser-based reaction tests and hardware checks with a five-round score and an optional weekly leaderboard.
- My role
- Product design, development & launch
- Built for
- Curious visitors and people checking their setup
- Platform
- Web · JavaScript · Cloudflare Workers and D1
The job to solve.
A reaction test has to make its state unmistakable: when to wait, when to react and when an attempt was too early. It also needs to be honest about what browser measurements can tell someone.
The approach
ReactionCheck uses a simple wait-and-react loop with click, touch and keyboard input. Five rounds produce an average and best response, with a separate option to take part in the weekly board.
Take a closer look.
A 21-second visual tour made from real product screenshots. Captioned, with no audio. Press play when you’re ready.
Screen descriptions
- 0:00Wait, then react
The real desktop page shows the reaction-test surface and its instructions.
- 0:07Use touch or a key
The real mobile layout shows the same test on a narrow viewport. The product also accepts Space and Enter.
- 0:14Understand the score
Five attempts produce an average and best response, with optional participation in a weekly leaderboard.
What I built.
A lightweight interactive product where timing, input handling and clear feedback matter more than a large framework.
- An understandable test
- Random waits, early-input feedback and a five-round result form the core reaction workflow.
- More ways to explore
- The collection also includes F1-light and audio reaction tests, plus controller, mouse, FPS, spacebar and pixel tools.
- Optional public participation
- A weekly top 10 supports anonymous scores and an explicit choice to publish a name or brand.
Out in the world.
Results are browser measurements, affected by the device and input method. They are not medical assessments or independently verified performance scores.
Visit ReactionCheck9,480 requests served
Cloudflare · reactioncheck.com
30 days ending 30 September 2026.
Requests measure network activity, not unique visitors, customers or revenue.
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