Be Random

Be Random is a free online randomness test that asks a simple question: can you be random? You choose 32 coin flips, heads or tails, one at a time, and try to make them look exactly like a real coin did it. It sounds easy. It is not: people are famously bad at it. We avoid long streaks, we switch sides too often and we keep heads and tails too even, and a 1950s-style outguessing machine is waiting to show you exactly where your flips gave you away. A game takes about a minute, runs in your browser with no download, and sits happily among our quick games and brain games.

In round one the machine reads your tape and prints a report with real, exact statistics. Your longest streak is set against what 32 real coin flips give (a real coin runs to 5 or more in a row in 65% of runs, and to 4 or more in 92%), your switches against the coin's 50%, your heads and tails balance, and the pattern you repeated most. Each one is marked typical, plausible, unusual or rare for a real coin, the four add up to a randomness score out of 100, and the machine names the single biggest tell, like "You never let a streak go past 3. A real coin does in 92% of 32-flip runs." Every probability it prints is computed exactly over all 4,294,967,296 possible sequences of 32 flips, not estimated.

Round two is beat the predictor. The machine has read your first 32 flips, and before each of your next 32 it seals a guess. After you flip, the guess is revealed: CALLED IT or FOOLED IT, and its hit-rate needle moves. Against a real coin it could only ever be right half the time, but against people it is usually right about 60% of the time, because it keeps eight simple theories about how people flip (you switch, you repeat, you break streaks, you replay patterns) and trusts whichever has been right about you lately. At the end it tells you which theory worked best on you. Each day the machine runs a different program, its opening hunch about you, like the Gambler, who bets your streaks will break.

The best part is seeing everyone else. Played for fun, Be Random shows today's crowd: a chart of everyone's longest streaks beside a real coin's (people pile up at 3 and 4 in a row, the coin spreads out to 6, 7 and beyond), everyone's switching rate, how often the machine guessed people today and "more random than 72% of the people who took it today". Then the machine prints your report, a torn-off receipt with both tapes, both scores and the tell, made for a screenshot or the share button.

Your score is your randomness out of 100 plus the share of round two's flips that fooled the machine, so a perfect coin-like tape and a machine you fooled every time would make 200. Ranked runs are replayed and checked on our servers, so the leaderboard is fair; the crowd comparison is just for fun and never changes a score. Play it on a phone by tapping the big HEADS and TAILS buttons, or on a computer with the mouse or the H and T keys (the arrow keys work too). It is one of our casual games, plays on mobile and PC, and there is no way to lose: every run ends with a score and something you did not know about chance.