Can you fake a coin?
Type 50 flips that look random. The streaks will give you away.
Pretend you are a coin. Tap H or T fifty times (or press the H and T keys). Try to make it look truly random.
0 of 50 · heads 0
The verdict appears at 50
Two things give fakes away: how often you switch between H and T, and how long your longest streak is.
What’s going on
A fair coin switches sides only half the time. Fifty real flips average 25.5 runs (unbroken stretches of H or T), and their longest streak averages about 6. Fakes usually switch too often and dodge long streaks, so they come out too tidy.
The verdict is a hypothesis test. The null hypothesis is a fair coin with independent flips. Your page flips 20,000 real sequences of 50 and asks, for switches, longest streak and number of heads, how often a real coin lands at least as far from average as you did, in either direction. That share is a two-sided p-value.
Each test uses a 2% cutoff, so a truly random sequence gets flagged only about 3% of the time. Passing does not prove you are random; it means the test could not tell.