Utilore

Coin Flip

Press the button — the coin turns over in the air and lands on heads or tails. Both sides are exactly equally likely: the result comes from the browser's cryptographic random source, not from a shuffled list of pictures. Below the coin there is a running count and the longest streak, because a streak is what makes people doubt a fair draw.

Press the button — the coin spins and lands on its own.

Ready

Each flip is drawn from the browser’s cryptographic random source, and the two sides are exactly equally likely. The count below is there to be looked at, not to be predicted from: the coin has no memory, so after five heads in a row the sixth flip is still 50/50. A real metal coin is the less fair one — spun on a table it favours one side, and even a tossed coin lands on the side it started from slightly more often than half the time.

Nearby: Random Number Generator, Random Picker, Dice Roller, Password Generator

How to use

  1. Press «Flip the coin». The coin spins for about half a second and stops on the side that came up.
  2. To settle something between several people at once, pick a higher number of coins — up to a hundred fall in one throw and the result is reported as «so many heads, so many tails».
  3. The line below counts every flip in this tab: how many of each side, how many throws in total and what share came up heads.
  4. «Reset the count» clears the tally and the strip of past flips. The coin itself needs no reset — every flip is independent anyway.

Good to know

The count says nothing about the next flip

After five heads in a row it feels like tails is owed. It is not: the coin has no memory, and the sixth flip is still fifty-fifty. That feeling is common enough to have a name — the gambler's fallacy — and it is the reason the tool shows the longest streak next to the count. Long runs are not evidence of a broken draw; in a hundred honest flips a run of six is ordinary. What does even out over time is the share, and only slowly: after a thousand flips it usually sits within a couple of percent of half, not exactly on it.

A coin on the screen is fairer than a coin in your hand

A real metal coin is not perfectly fair. Spun on its edge on a table it clearly favours one side, because the rim is machined slightly unevenly. Even a coin tossed in the air lands with the same face up as it started about 51 % of the time — it wobbles around an axis rather than turning end over end. Those are small biases, but they are real and they are physical. A digital flip has no rim and no wobble: the two outcomes are equal by construction.

Where the randomness comes from

Each flip reads one bit from crypto.getRandomValues, the browser's cryptographic random source, which is the same source used for keys and session tokens. The usual Math.random is not used here: its output can be predicted from a handful of previous values, and while that hardly matters for an animation, it matters for a draw where something is at stake. The draw is made in your tab and never leaves it — the page works with the network switched off.

Frequently asked questions

Is it really fifty-fifty?

Yes, exactly. One random bit decides the side, and both values of that bit are equally likely. There is no weighting, no «make it interesting» correction and no hidden pattern — feed the tool a few thousand flips and the share will sit near 50 %, drifting a little the way an honest draw does.

Five heads came up in a row. Is tails now more likely?

No. Every flip starts from scratch and knows nothing about the previous ones, so the next one is still 50/50. Runs like that are normal: in a hundred flips a run of five or six turns up more often than not.

Can I flip more than one coin?

Yes, up to a hundred in one throw. That is handy when several people need an answer at once, or when you want to see for yourself how the share behaves: a hundred coins at a time gets you to a thousand flips in ten presses.

Is the result sent anywhere?

No. The flip happens in this tab, and nothing about it is sent, stored on a server or logged. The page works offline, and closing the tab erases the count.

Can we use it to decide something for real?

That is what it is for, and it is fairer than the coin in your pocket. For a decision between people, do what you would do with a real coin: agree on which side means what before the flip, and let everyone watch the same screen.

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