Flip a Coin — Heads or Tails, Provably Fair

A genuinely fair coin from your browser's cryptographic random number generator, with a tally so you can see it is 50/50.

🔒 Runs in your browser — files never uploaded ⚡ No signup 💯 Free

0Heads
0Tails
0Flips
—Heads share
—Current streak

Flip a coin online. Each flip is decided by the browser's cryptographic random number generator — the same source used for encryption keys — so heads and tails are exactly equally likely and nothing about the previous flip affects the next. Flip one coin or up to a hundred at once, and watch the running tally and the current streak.

How to use Coin Flip

  1. Tap the coin or press Flip.
  2. To flip several coins at once, set the number; you get each result and the totals.
  3. The tally keeps counting until you reset it.

Fair means fair

A "random" function in most software is a pseudo-random generator seeded from the clock: fine for a game, but predictable in principle. This coin uses crypto.getRandomValues, the browser's cryptographically secure generator, and maps it to two outcomes with rejection sampling so neither side gets a rounding advantage. Over a few hundred flips the heads share settles close to 50% — the tally is there so you can see it happen.

Streaks are normal

Five heads in a row happens about once every 32 runs of five. Ten in a row is rare (one in a thousand) but not remarkable across a long session. A coin has no memory: after five heads, the chance of another is still exactly one half. If a streak feels wrong, that feeling is the gambler's fallacy, and it is the reason the streak counter is on the page — to make the ordinary size of streaks visible.

Real coins are less fair

A physical coin caught in the hand lands the same way it started about 51% of the time, because of the physics of the wobble, and some coins are slightly biased by their design. A coin spun on a table is worse — the heavier side wins more often. If you are settling something that matters, the browser coin is the fairer instrument.

For more sides, the dice roller; for choosing among names or options, the random picker.

Frequently asked questions

Is the coin really 50/50?

Yes. Each flip takes a 32-bit value from the browser's cryptographic generator and maps it to two outcomes with rejection sampling, so there is no rounding bias. Flip a few hundred times and the heads share converges on 50%.

I got heads five times in a row. Is something wrong?

No — five in a row happens about one run in thirty-two. A coin has no memory; after any streak the next flip is still 50/50. The streak counter is there to show how ordinary streaks are.

Can I flip more than one coin?

Up to 100 at once. You get every individual result and the heads/tails totals for that batch, and all of them go into the running tally.

Does it work offline?

Yes. Once the page has loaded, nothing else is fetched — the randomness comes from your device.

Is a real coin fair?

Close, not quite: a caught coin lands the way it started about 51% of the time, and spinning a coin on a table favours the heavier side noticeably. The browser coin is fairer than the one in your pocket.

Related tools

Dice Roller Roll any dice with standard notation like 2d6+3 or 4d6dl1, see every die, and keep a history — fair rolls from cryptographic randomness. Yes or No Ask a question, get a yes or a no (or a maybe, if you allow it) — decided by a cryptographically fair random draw. Random Picker Pick a winner from a list, choose several, shuffle the order, or split into teams. Random Number Generator Generate random numbers in any range, with or without repeats. Random Word Generator Draw random words from a 359,000-word dictionary — common words for games and prompts, or the whole list — filtered by length and first letters. Random Name Generator Generate up to 200 realistic names at once — mixed, female or male, with optional middle initials — for test data, characters and placeholders.