Coin Flipper
Flip a fair coin, one at a time or a thousand at once, and watch the tally.
About the Coin Flipper
Each flip comes from the browser's cryptographic random source with the modulo bias removed, so it is genuinely 50/50 — not approximately, and not dependent on Math.random, which is not designed to be unpredictable.
The streak counter is there because it is where intuition fails hardest. In 100 fair flips, a run of six the same way happens more often than not, and people read that as evidence the coin is rigged. It is not; genuinely random sequences are far more clustered than invented ones.
Flipping a few thousand at once shows the law of large numbers doing its work: the percentage settles towards 50 as the count rises. It says nothing whatever about what the next flip will do, which is the gambler's fallacy in one sentence.
How it works
Press flip. The result uses the browser's cryptographic randomness, not Math.random.
Flip many at once to see the tally converge on 50/50.
The running history and streaks are kept for the session.
Frequently asked questions
- Is this coin flip actually random?
- Yes. It uses the Web Crypto API rather than Math.random and rejects the biased portion of the range, so heads and tails are exactly equally likely on every flip.
- Why do I keep getting the same result?
- Because streaks are normal. In 100 fair flips a run of six is more likely than not, and genuinely random sequences look far more clustered than people expect. A run is not evidence of bias.
- If I get five heads, is tails more likely next?
- No. The coin has no memory — the next flip is 50/50 regardless of what came before. Believing otherwise is the gambler's fallacy, and it is the single most expensive misconception in probability.
- Can I flip many coins at once?
- Yes, up to ten thousand. Watching the percentage settle towards 50 as the count rises is the law of large numbers made visible.
- Is a real coin flip actually 50/50?
- Close, but not exactly. Physical coins are slightly biased towards the face they started on, and a spun coin is more biased still. A cryptographic random source has no such physical asymmetry.
Privacy
Everything happens locally. Your files are read by your own browser, processed on your device, and never uploaded — closing the tab is all it takes to erase them.
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