Coin Flip

Flip a virtual coin online. Heads or tails with a 3D animation, plus a batch flipper, running tally and streak stats. Crypto randomness, in your browser.

🌐 Español

Press Flip to toss the coin.

Flip many coins at once

Flip a whole batch instantly and read the heads/tails tally and streaks — try 10, 100, or 1,000 coins.

Each flip is an independent, fair 50/50 draw from your browser's cryptographic random generator. Past flips never change the odds of the next one. History lives only in this tab and is gone when you reload — nothing is saved or uploaded. Batch flips support up to 10,000 coins.

🔒 Private by design: everything runs locally in your browser and never uploaded to any server.

Written and maintained by Last updated

One draw from the browser’s cryptographic generator per flip

Every flip on this page is a single integer drawn from crypto.getRandomValues, the browser’s cryptographically secure random source, the same one used to generate keys and passwords, rather than Math.random.

The draw is also unbiased in the way that trips up naive implementations. Taking a random 32-bit word and reducing it with a modulo is skewed whenever the range does not divide evenly into the word space, so the shared helper behind this page uses rejection sampling instead: a word landing in the uneven tail is discarded and another is drawn. For a two-outcome draw a modulo would in fact have been fine, but the unbiased helper is used anyway, which is what lets the same wording apply here, on the Dice Roller and on the Random Number Generator alike.

Zero maps to heads, one maps to tails. There is no weighting, no house edge and no memory.

The spin is theatre over a decision already made

The 3D coin animation runs for about nine tenths of a second and decides nothing. The result is drawn first, and the rotation is then computed to land on that face: the coin spins forward by between four and a half and five and a half turns, snapping to the half-turn parity belonging to the side already chosen.

So nothing about how you press the button matters. Holding it down, tapping it fast, or clicking during the spin (the button is disabled while the coin is in the air, so that one does nothing at all) changes no odds. An animated flipper invites exactly that suspicion, and the honest answer is that the animation is a reveal rather than a simulation of physics.

Flipping one at a time, then a thousand at once

  1. Click Flip coin and wait for the coin to settle on Heads or Tails.
  2. Keep flipping; a tally, a percentage split and a streak line appear under the coin from the first result onward.
  3. For a batch, type a figure into Number of coins and click Flip coins, or just press Enter.
  4. Use Reset tally to clear the running single-flip session.

The batch box opens on 100 and takes any whole number from 1 to 10,000. Ask for zero, ask for more than the cap, or leave the box empty, and this widget prints the actual reason in place of a result rather than the generic failure banner most tools here fall back on. A decimal is truncated to its whole part rather than refused, so 5.7 flips five coins.

A batch reports the heads and tails counts, each side’s percentage, the total, the longest run in the sequence and the longest run of each side separately. It also prints a strip of H and T letters, capped at the first 500 so a huge batch does not put ten thousand elements into the page.

Current streak and longest run answer different questions

Two streak numbers sit under the tally and they get mixed up constantly.

The Current streak figure is the run at the end of the sequence: how many identical results have landed in a row right now. It drops back to one the moment the other side comes up.

The Longest run figure is the biggest run of consecutive identical results anywhere in the sequence so far, and it never goes down. Alongside it are separate longest-heads and longest-tails figures, which are the pair to look at when a session feels lopsided.

They are on screen because streaks are the single most misread thing about randomness. After five heads it feels like tails is due. It is not: a coin has no memory, each draw is independent, and the sixth flip is exactly 50/50 again. Flip a thousand coins in the batch box and you will usually find a run far longer than intuition says is reasonable, which argues against chasing streaks better than any explanation does.

Percentages that will not always add up to 100

The two percentages are each rounded to one decimal place independently, and independent rounding does not have to sum to exactly 100. Most splits behave, since a one-in-three split shows 33.3 and 66.7, but others land on 99.9 or 100.1. That is an artefact of rounding twice, not a counting error: the underlying counts always add up to the total exactly.

The related thing to expect is that a large batch lands near 50 percent without landing on it. A thousand-coin batch that came out exactly even every time would be evidence of something wrong. Watching the drift shrink as you move from 10 coins to 100 to 1,000 is about the clearest demonstration of the law of large numbers you can get in four clicks, which is why this page is as useful in a classroom as it is for settling who buys lunch.

Two tallies, and only one of them the reset button touches

The single-flip session and the batch flipper keep separate results. Reset tally clears the running single-flip sequence only; whatever the batch panel last produced stays on screen until you run another batch, so a 1,000-coin batch never pollutes the counts under the coin.

Both live in the tab’s memory and nowhere else. There is no account, no history file, no server call and nothing written to disk, so reloading discards every flip you have made. If the tally itself is the point, write the numbers down before you refresh.

For more than two outcomes, the Wheel of Names spins over a list you type; the rest are on the generators hub.

See it in action

Screenshot of the Coin Flip tool with a single coin waiting to be tossed for heads or tails, alongside a batch mode that flips 10, 100 or 1,000 at once and reports the heads/tails tally and the longest streaks
Coin Flip mid-process: a single coin waiting to be tossed for heads or tails, alongside a batch mode that flips 10, 100 or 1,000 at once and reports the heads/tails tally and the longest streaks.
Diagram: where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen
Where the work happens on a SysFenix page that has no file input at all: the tool arrives as ordinary JavaScript inside the page, works the answer out on your own device and renders it in place, so the upload, queue and server-side record a typical online tool needs never happen.

Frequently asked questions

Does Reset tally clear the batch result too?

No. It clears only the running single-flip sequence under the coin. Whatever the batch panel is showing stays on screen until you flip another batch, because the two are separate sequences with separate tallies and nothing merges them. Reloading the page is what clears both, along with everything else.

Why do the heads and tails percentages sometimes add up to 100.1?

Each percentage is rounded to one decimal place on its own, and two independently rounded values are not obliged to sum to a round number. The raw counts are exact and always add up to the total shown; only the two displayed percentages can drift by a tenth. It is a rounding artefact in the display and never affects a flip.

A batch of 10,000 only shows a few hundred H and T letters. Where are the rest?

The visual strip is capped at the first 500 outcomes so a huge batch does not build a huge amount of page structure, and a note underneath tells you how many of the total are drawn. Every figure above the strip, the tally, the percentages and all the streak numbers, is computed from the entire batch rather than from the visible part.

If two runs tie for longest, which one is reported?

The earlier one. When a later run matches the record it does not replace it, so the side named is whichever got there first. That is a tie-break chosen so the number stays stable while you keep flipping, and it carries no statistical meaning of its own.

Can I weight the coin, or add a third outcome?

No. This is deliberately a fair two-outcome draw with nothing to configure except how many coins to flip. For a weighted or many-sided decision you want a different shape of tool: a range draw, a dice expression or a named wheel all express that properly, and keeping this page unconfigurable is what lets the fairness claim stay simple and true.

Can I flip again while the coin is still spinning?

No. The button is disabled for the length of the animation, roughly nine tenths of a second, and its label changes to a Flipping notice while it runs. That is a user-interface decision rather than a statistical one, since the result was drawn before the spin started. If you want many results quickly, the batch box produces them instantly using exactly the same per-coin draw.

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