Coin Flip
Toss a coin in the browser: heads or tails from a cryptographic random generator, with a best-of series and up to ten coins.
Last 20 results
Nothing yet. Every flip is added here, newest first.
How to use
- Step 1Tap the coin, or press Space. It tumbles for about a second and lands on one of the two sides; the result is also written under the coin and read out to screen readers.
- Step 2Settling something over several tosses? Switch Best of to 3, 5 or 7 and the running score is kept until one side reaches the majority.
- Step 3For a kickoff, put the two team names on the sides in Settings. To toss a handful at once — a probability lesson, a quick sample — set Coins at once up to ten and read the tally.
When a coin toss is the right tool
A toss is for the decisions where the two options are close enough that arguing costs more than choosing. It settles who starts, and it settles a tie without anyone having to give way; that is why it survives in sport, in board games and in a kitchen at dinner time.
There is a second, sneakier use. Toss the coin for a decision you have been circling for days, and pay attention to what you hope to see while it is in the air. The coin does not decide anything — it just makes you notice which answer you already wanted.
- Kickoff, first serve, ends of the court or first bat.
- Who goes first in a board game, a quiz or a pitch order.
- Splitting a tie when two answers or two teams end level.
- Choosing between two options that are genuinely equal in value.
- Teaching probability: ten coins at once, twenty times, and the class can see the shape of the tally.
Is this flip fair?
Yes, and in a narrow, checkable way. Every toss asks the browser for a fresh random byte from crypto.getRandomValues — the same generator used for cryptographic keys, seeded by the operating system — and reads its lowest bit. Of the 256 possible byte values, exactly 128 are even and 128 are odd, so the two sides are equally likely with no remainder to bias one of them.
The result is decided before the animation begins; the tumbling coin is just a picture of a choice already made. Nothing is sent to a server, nothing about your tosses is stored anywhere but this browser, and no earlier result changes what the next one can be.
A real coin is slightly less fair than that. A 2023 experiment that recorded 350,757 tosses by hand found that a coin lands the same side up as it started roughly 51% of the time, because a thumb-flipped coin wobbles as well as spins. A browser has no thumb, so the bias has nowhere to come from.
Streaks: why five heads in a row is normal
The history keeps your last twenty results, newest first, with the totals and the run you are currently on. It exists mostly to settle arguments about streaks, because people badly underestimate how common they are.
Any particular sequence of five tosses has a 1-in-32 chance — and that is just as true of heads-tails-heads-tails-heads as it is of five heads. The difference is that you notice one of them. Across twenty tosses, a run of four or more of the same side turns up about three times in four, and a run of five or more in nearly half of all sets of twenty.
The other half of the same coin: the totals are not supposed to be level. Twenty tosses landing 12–8 is ordinary; an exact 10–10 happens only about 18% of the time. A generator that produced neat, alternating, evenly balanced results would be the broken one.
Best of three, five or seven
In series mode the coins drop to one and the score is kept for you: each toss goes to one side, and the series ends the moment one of them has the majority, exactly as a real best-of does. A best of five that stands at 3–0 is over, so the board stops instead of tossing two meaningless extra rounds.
| Series | First to | Most tosses it can take |
|---|---|---|
| Best of 3 | 2 | 3 |
| Best of 5 | 3 | 5 |
| Best of 7 | 4 | 7 |
Questions and answers
Is the result really random, or is there a pattern?
It comes from crypto.getRandomValues, the browser's cryptographic random generator, one fresh byte per toss with its lowest bit used as the side. There is no seed you could work out, no pattern to follow and no memory of earlier tosses.
Can I use it to decide something that matters?
For a two-way choice between people in the same room, yes — everyone watches the same screen. For anything with real value at stake, remember that people who are not in the room cannot verify what happened on your device; draw prizes in front of the participants, or on a stream.
Can I put team names on the coin instead of heads and tails?
Yes. Open Settings and type the two names; they are drawn on the two faces and used in the result, the history and the series score. Names are cut to 20 characters so they still fit on the coin, and an empty name falls back to Heads or Tails.
Why did it give me six heads in a row?
Because runs are much more common than they feel. Each toss is independent, so after five heads the next toss is still an even 50/50 — a coin has no way to remember and no obligation to even things out.
What does flipping ten coins at once do?
It tosses ten independent coins and shows the tally of the two sides. It is the quickest way to show a class that ten coins rarely land 5–5, and it also works as a quick random sample when you need several yes/no draws at the same time.