Flip a Coin

Transparent randomness

How this online coin flipper works

The result is chosen before the animation begins. Your browser fills a 32-bit unsigned integer with crypto.getRandomValues(). Values below the exact midpoint become heads; values at or above it become tails.

1. Create one 32-bit value.The possible range is 0 through 4,294,967,295.
2. Split the range evenly.Each side receives exactly 2,147,483,648 possible values.
3. Animate the chosen result.The visual coin cannot change the already selected side.

const value = new Uint32Array(1);
crypto.getRandomValues(value);
const isHeads = value[0] < 0x80000000;

For implementation details, see the MDN Web Crypto reference and the W3C Web Cryptography specification.

Is a coin flip really 50/50?

This simulator is designed as an exact 50/50 digital choice. Physical tossing is more complicated. A large experiment involving 350,757 physical flips found no overall heads-versus-tails bias when the starting side was randomized, but it did find a small tendency for a coin to land on the same side it started. Read the published coin-toss study record.

Short runs can still look uneven. Five heads in a row does not make the next flip more likely to be tails. Use the streak calculator to measure how surprising a run is.

Useful ways to flip a coin

Do not use a random result for medical, legal, financial, safety, or other high-impact decisions.

Coin flip questions