Coin Flip

What this coin flip does

So you need to settle something and you do not have a coin on you. That is what this is for. Press the button, or tap the coin itself, and it lands on heads or tails. It keeps a running count of how many heads and tails you have got so far, and the Reset button puts that back to zero whenever you want a fresh tally. That is the whole tool. No sign up, nothing to install, it just flips.

How to use it

1. Press Flip Coin, or click the coin, and watch it spin.
2. Read the result when it lands, heads or tails.
3. Keep flipping if you need best of three, the running count keeps score for you.
4. Hit Reset any time to clear the count and start over.

It pauses for a few seconds while the coin spins, so give it a moment between flips.

Is it actually a fair 50/50?

So is it actually fair? Yes. Every flip uses your browser's built in random number generator, Math.random, to pick one of two outcomes with an even chance each. There is no pattern, there is no memory of past flips, and there is no way to predict the next one. Over many flips, heads and tails each come up about half the time. All of it runs on your own device, and nothing is sent anywhere.

One honest footnote, the kind I like to be straight about. Math.random is what is called pseudo random. It is an algorithm rather than physical noise. For flipping a coin to decide who buys lunch, it is perfectly fair and you will never spot a pattern.

A real coin vs this one

Here is something most people do not know. A real coin is not a perfect 50/50. In 2023 a group of researchers flipped actual coins 350,757 times to test a physics prediction from 2007, and the coins landed on the same side they started about 50.8 percent of the time. The reason is a tiny wobble your hand adds when you flip, which keeps the starting side facing up a little longer. It is small, but it is real.

The funny part is that a virtual coin like this one does not have that problem. There is no wobble, no starting side, no hand. It is just two outcomes with an even chance, so in a way this is the cleaner 50/50. If you ever flip a real coin and want it properly fair, the trick is simple, do not let anyone see which side was facing up to start.

What people use a coin flip for

A coin flip is the quickest tie breaker there is. People use this one to decide who goes first in a game, to settle a small argument, to choose between two options for dinner, to do the kickoff in a backyard match, or just to make a call when both options are fine and they are tired of thinking about it. If you flip it and feel a flash of disappointment at the result, pay attention to that. It usually means you already knew which one you wanted.

Questions people ask

References

1. Bartoš, F., et al. Fair coins tend to land on the same side they started: Evidence from 350,757 flips (2023). https://arxiv.org/abs/2310.04153
2. Diaconis, P., Holmes, S., and Montgomery, R. Dynamical Bias in the Coin Toss. SIAM Review, 49(2), 211 to 235 (2007). https://doi.org/10.1137/S0036144504446436
3. MDN Web Docs. Math.random(). https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/random