Coin Flipper — Heads or Tails
Flip a coin
How it works
This coin flipper uses client-side randomness. If supported, it prefers crypto.getRandomValues for uniform, unbiased bits; otherwise it falls back to Math.random(). No data leaves your browser.
Tips
- Space — Flip.
- Shift + Space — Best-of-N with your chosen N (must be odd).
- Esc — Clear history.
FAQs
Is it 50/50? Yes—results are uniformly random. Multi-flip tallies reveal natural streaks that still occur in fair sequences.
Coin flipping 101: fairness, history, and smart use
Coin flipping—often phrased as “heads or tails”—is one of the simplest ways to generate a random binary outcome. With a fair coin, each side has a probability of 0.5, and successive flips are independent: what happened before does not influence the next result. That independence trips people up; long streaks of Heads or Tails occur naturally and don’t imply bias.
Why it’s (almost) 50/50
In theory, a perfectly symmetric coin with a perfectly symmetric flip is exactly 50/50. Real coins and human flips introduce tiny biases (weight distribution, spin, air currents), but vigorous, unconstrained flips still produce outcomes very close to even. Digital coin flippers like this one simulate a uniform random choice in your browser, optionally using cryptographic randomness for extra assurance.
Quick probability intuition
- Single flip: 50% Heads, 50% Tails.
- Best of 3: the chance that Heads “wins the series” is still 50% when the coin is fair, but variance is reduced compared to a single flip.
- Streaks: The probability of k Heads in a row is (1/2)k. Seeing four Heads isn’t suspicious—it should pop up about once every 16 flips on average.
- Law of Large Numbers: Over thousands of flips the Heads % drifts towards 50%, but short runs can look lopsided.
Everyday uses (UK/EU & beyond)
Coin tosses settle start-player decisions in playground games, choose who serves in tennis, and help captains decide ends or kick-off in football. Courts and committees sometimes use a coin to break ties where two options are genuinely equal. In product design and A/B testing, a “coin flip” is the mental model for random assignment, ensuring comparisons are fair.
Best practices
- State rules first: e.g., “Best of 1; Heads = Team A chooses end.”
- Use odd counts for series (best-of-3, best-of-5) to avoid draws.
- Avoid confirmation bias: don’t stop early only when your preferred side is ahead—commit in advance.
Fun fact
Mass coin-toss events have been organised at sports grounds and festivals for charity and publicity, demonstrating how quickly randomness scales when lots of people flip at once. Whether one coin or many, the mathematics is the same—each heads or tails outcome is an independent trial from a Bernoulli distribution (p = 0.5).
Bottom line: for fast, transparent decision-making, a coin flip is hard to beat—simple to explain, easy to verify, and statistically sound.