How to use it
- Press Flip, tap the coin or press Space.
- Watch the coin spin in the air and land on heads or tails.
- Keep flipping to see the tally, percentages and current streak in the panel. Press Reset to start a new count.
When to flip a coin
A coin toss is the oldest fair way to settle a two-way choice. Who kicks off, who picks the movie, which restaurant, who takes the first turn: when both options are fine and nobody wants to decide, a coin does it instantly. This virtual coin is always in your pocket, works the same on a phone or a projector, and can’t be “accidentally” caught or thrown badly.
In class and at home
- Teaching probability. Ask students to predict how many heads they’ll get in 20 flips, then flip together and watch the tally. Do it again with 100 flips and compare the percentages.
- Streaks. Ask the class how likely five heads in a row is before trying it. Most people underestimate how often streaks happen.
- Fair turns. Settle who starts a game, who answers first or which team chooses the side of the field.
- Quick decisions. Tea or coffee, stay in or go out. If you catch yourself hoping for one side while the coin is in the air, you already know your answer.
How the flip is decided
When you press Flip, the result is chosen first with crypto.getRandomValues, the cryptographically secure random number generator built into your browser, and not with the weaker Math.random(). Only then does the 3D animation start: the coin is launched with a few full turns and is set to finish showing the side that was already chosen. The number of turns changes from flip to flip so it looks natural, but it has no effect on the result.
We test the coin automatically every time the site changes: 100,000 simulated flips must come up heads between 49% and 51% of the time.
Heads, tails and a bit of history
People have been deciding things with coins for more than two thousand years. The Romans called it “navia aut caput”, ship or head, after the two sides of their coins. In the United States, coin tosses decide who kicks off in football games, and in some elections a coin toss has been used to break an exact tie. Today most toss-ups happen on a phone, but the rule is the same: two sides, one flip, no arguments.
Frequently asked questions
Is this virtual coin flip really 50/50?
Yes. Each flip is decided with your browser’s cryptographic random number generator before the animation starts, and heads and tails have exactly the same chance. Automated tests flip the coin 100,000 times and check that heads lands between 49% and 51% of the time. The 3D animation is then built to land on the side that was already chosen.
Is a real coin toss fair?
Almost. Research on real coin tosses has found a slight tendency to land on the same side that was facing up at the start, around 51%. A virtual flip doesn’t have that bias, because it doesn’t depend on how you throw.
I got heads five times in a row. Is something wrong?
No. Streaks are completely normal. In 100 flips, a run of five or more of the same side is very likely to happen. Each flip is independent: the coin doesn’t remember the last result, so after five heads the next flip is still exactly 50/50.
What does the tally show?
How many times each side came up in this session, the percentages, and your current streak. The more you flip, the closer the percentages usually get to 50%, which is a nice way to see the law of large numbers in action.
Can I use it without internet?
Yes. Once the page has loaded, it doesn’t need a connection, and nothing about your flips is sent anywhere.