Coin flip

Flip one coin, or a hundred at once. The tally keeps count across the session and is still here next time you open the page.

How it works

Each coin is a separate draw with two equally likely outcomes, taken from crypto.getRandomValues — your browser's built-in generator for security work. Flipping twenty coins is twenty independent draws rather than one number sliced into twenty pieces. Slicing would be faster and would turn the independence of each coin into an argument about the generator rather than something the code makes plain.

There is no simulated physics, no weighting, and no memory between flips. A coin here is a coin: two outcomes, equally likely, every single time.

What the tally is, and what it is not

The tally counts what has already happened — flips, heads, tails, and the longest run of one face within a single throw. It is a record, and it is genuinely interesting to watch. What it is emphatically not is a hint about the next flip. Every flip is independent of every flip before it, so a run of six heads leaves the next flip at exactly even, the same as the first one was.

The longest run is measured within a throw rather than across throws, because ten separate flips of one coin and two throws of five coins are different things. Joining them would report a run that never actually happened in one sequence.

Worked examples

Settling something between two people

One coin, one flip, and the answer is on screen in text rather than in an animation somebody has to interpret. If the decision is between more than two options, the wheel is the better tool and the link is at the bottom of this page.

Watching what randomness actually looks like

Flip a hundred coins at once. Most people expect something close to fifty-fifty with the heads and tails fairly evenly mixed, and are surprised by how often a run of five or six of the same face turns up. Runs like that are ordinary rather than remarkable, and seeing them is the quickest cure for the feeling that a result is somehow overdue.

Assigning sides or turns

Flip once per person and read the sequence. For anything more elaborate — splitting a group, putting people in an order — there are tools on this site built for exactly that, and they keep your list between visits.

Questions people actually ask

I have flipped six heads in a row. Is tails due?

No. The next flip is exactly even, just as the first one was. A coin has no memory, and nothing about the previous six flips changes anything about the seventh. This is the single most common misunderstanding about randomness, and a tool that hinted otherwise would be telling you something untrue. The tally on this page is a record of the past, not a forecast.

There is a second half to that answer, and it is the more interesting one: a run of six is not even unusual. People ask whether tails is due because a run that long feels like it needs explaining. It does not. In a series of 100 flips, a run of six or more of the same face turns up 81% of the time — it is the normal case, not the strange one.

How long a run should you actually expect?

Here is the whole picture for a series of 100 flips. Each row is the chance that somewhere in those 100 flips there is a run of at least that many identical faces in a row.

The longest run you are more likely than not to see in 100 flips is 7. So if you flip a coin a hundred times and the longest streak you get is seven heads, nothing has gone wrong — that is the single most ordinary outcome there is.

Series length matters more than people expect, and it is the part that trips up the intuition. The same run of 6 that appears 81% of the time in 100 flips appears only 24% of the time in 20. A long run is not evidence that a coin is unfair; it is mostly evidence that you flipped it a lot of times.

These are exact figures rather than estimates, calculated the same way every time this page is built, and the calculation is checked against a count of every possible sequence for the shorter series. We publish the method for the same reason we publish the shuffle measurements: a claim about randomness is worth what its working is worth.

Is the coin actually fair?

Yes. Both outcomes are equally likely on every flip, drawn from your browser's cryptographic generator. Over a long enough session the share of heads will sit near half, but it will wander either side of it on the way — and it is not being corrected toward half by anything.

Is my tally sent anywhere?

No. The flipping happens inside your browser and the tally is stored on your own device using your browser's local storage. Nothing is uploaded and no server here ever sees a flip.

Why would I use this rather than the box in the search results?

For a single flip, honestly, you would not — and it would be silly to pretend otherwise. This page is worth opening when you want more than one coin at a time, or a tally that survives the tab being closed. Both are things an inline widget does not do.

Limitations, stated plainly

• A hundred coins at once is the ceiling.
• The tally is tied to one browser. It does not follow you to another device, because there is no account and nothing is stored on a server.
• There is no history of individual throws — only the running totals and the best run. If you need every throw recorded, the dice roller keeps a full history.
• No sound and no animation. The result is text, immediately.