ODDLY LIKELY
ODDLY LIKELY
In each round, one pattern comes from a true random generator. The other was made the way people fake randomness. Pick the real one. Six rounds, new patterns every time.
100 coin flips each. Yellow is heads, grey is tails. Which list is real?
Tap heads or tails 100 times, as randomly as you can, without using a real coin. Then see if your list passes for real.
0 / 100 · undo · start over
| Your list | Typical real list | |
|---|---|---|
| Longest streak | — | 7 (5 or more in 97% of lists) |
| Times it switched side | — | About 50 out of 99 |
| Heads | — | Usually between 40 and 60 |
Asked to be random, people try to make every stretch of the list look balanced. They switch between heads and tails too often, and they avoid long streaks because a streak "doesn't look random".
Real randomness doesn't care how it looks. In 100 fair coin flips, the chance of at least one run of 5 or more of the same side is about 97%, and a run of 6 or more shows up about 81% of the time. The longest run is usually around 7.
The same thing happens in two dimensions. Truly random stars clump together and leave empty gaps; faked ones are spread too evenly. And real dice land on the same number twice in a row about once every six rolls. Fakers avoid those doubles.
The real side uses your browser's random number generator every time you play. The fake side is generated by a rule that copies how people fake randomness: it switches side about two times in three and never allows more than three in a row (coins), spreads stars on a loose grid (stars), and never repeats a number back to back (dice). Both are made fresh for every round.
Coin flips, starry skies and dice: short videos that make you guess first, then explain the giveaway.