Flip a Coin

The simulator gives you a heads-or-tails result drawn from your browser's cryptographic random number generator — specifically crypto.getRandomValues, the Web Crypto API. Every flip pulls a fresh 32-bit unsigned integer and checks whether it's even or odd. Even goes to heads; odd goes to tails. There is no server call, no stored seed, and no animation rigging the outcome. The result is decided the instant you press Flip.

Why use a digital flip instead of a real coin?

A real coin is close to fair, but not exactly. The side facing up when you start the flip has a slight edge, the surface you catch it on changes the bounce, and how you toss it changes the spin. None of that is dramatic, but it's measurable. A digital flip removes those small physical biases — at the cost of trusting the code, which is why the source of randomness matters. We dig into the difference on the probability of a coin flip.

What the stats counter is for

The four numbers under the coin track your session: total flips, heads, tails, and the running heads percentage. Watch what happens as the count grows. With a small number of flips you'll often see lopsided results — eight heads and two tails out of ten is not unusual. Past a few hundred flips the percentage settles close to 50% and stays there. That's the law of large numbers at work, and it's the single biggest source of confusion about coin flips. We unpack it on law of large numbers in coin flipping.

When a coin flip is the right tool

A coin flip suits two kinds of decisions: when both options are roughly equal (and the deciding cost is not picking quickly), and when both parties want a procedurally fair outcome with no negotiation. It's a poor tool for decisions you actually have a preference about — picking up the coin and feeling disappointed by the result is a sign that you already knew the answer. For more nuance and for comparisons with dice, spinners, and number-pickers, see coin flip vs. other random pickers.

Last reviewed: April 25, 2026