Coin Flipper

What it does

Flip a coin online — one toss for a quick heads-or-tails decision, or up to 10,000 flips for a probability experiment. The Coin Flipper simulates a fair coin by default, lets you weight it (set the probability of heads anywhere from 0 to 1), and reports every individual result along with heads/tails counts, percentages, and streaks. Reuse a seed to reproduce an experiment exactly.

Common use cases

• Quick decisions — heads or tails, settled instantly, no coin required.
• Teaching probability — flip 10, 100, or 10,000 coins and watch the heads percentage converge toward the true probability (the law of large numbers, live).
• Weighted-coin experiments — set heads to 0.7 and compare the observed frequency against the configured bias.
• Simulations and testing — seeded flips make Bernoulli-trial fixtures reproducible in tests and demos.

Settings

• Flips — from a single toss up to 10,000 flips in one run.
• Heads probability — 0.5 is a fair coin; anything else is a weighted coin. At 0 or 1 the outcome is certain (useful for edge-case tests).
• Seed — leave blank for a fresh run every time, or set one to make the full sequence of flips repeatable.

Privacy note

Every flip is generated locally in your browser — results are never uploaded, logged, or stored on a server. Outcomes are simulated coin tosses, not physical ones.

FAQ

Is an online coin flip really 50/50? At the default setting, yes: each flip is an independent draw with a 0.5 probability of heads. Over a small number of flips the observed split can easily be 60/40 — that’s variance, not bias. Flip more coins and the percentage approaches 50%.

Can I flip more than one coin at a time? Yes — set the number of flips up to 10,000. The output lists every flip plus summary counts, percentages, and the longest streaks.

What does the seed do? Is a seeded flip still random? A seed makes the sequence deterministic pseudorandomness: the same seed and settings always reproduce the same flips. That’s ideal for repeatable experiments and tests, but it is not a security feature — don’t use seeded flips where the outcome must be unpredictable to others.

Can I make the coin unfair? Yes — that’s the heads-probability setting. It’s a legitimate teaching tool: compare a 0.5 coin with a 0.7 coin over 1,000 flips and the difference is obvious in the summary.