About TossThatCoin

TossThatCoin does one thing. It tosses a coin, it tells you which face came up, and it keeps a tally while you keep tossing. It is published by Sumvia, the team behind the Sumvia.net network of browser-native utilities, and it is the two-outcome sibling of SpinThatWheel.net, which handles every decision with more than two answers.

Why a whole site for a coin

Because the interesting part of a coin toss is not the coin — it is whether the toss was fair, and almost nothing that offers you a flip online is willing to explain how it decided. A coin toss settles arguments only as long as both parties trust the mechanism, so the mechanism is what this site documents: where the randomness comes from, in what order things happen, and what the animation is and is not doing. If you read one page here, read the methodology page; it is the actual product.

What it does

A single coin, tossed as many times as you like. You can simply toss it, or you can call it — either before the flip, the way a supervised pregame toss works, or in the air, the way it works on every playground and in cricket. Both conventions are real, they exist for different reasons, and the site supports both. Alongside the result it keeps a running tally: heads, tails, your longest run of one face, and — if you have been calling — how often you called correctly. That last number is the honest one. It will sit near half.

Who it is for

Anyone settling who goes first, who pays, who takes the awkward errand, or which of two equally reasonable options to stop arguing about. It is also for the person who suspects the flip was rigged, which is a more common reason to look up a coin toss than you might expect — and the reason the tally, the streak count, and the explanation of what real randomness looks like are on the page rather than buried.

Fairness is a claim, so it is tested

The draw is a small typed function with automated tests that feed it fixed byte sequences and check the exact mapping, including that a draw landing outside the range is discarded and redrawn rather than folded back in. Other tests confirm that the rotation the coin lands on always shows the face that was drawn — the invariant the entire animation depends on. Claiming a coin is fair is easy; the tests are there so the claim is checkable.

Browser-native, no accounts

There is no account, no upload, and no server application. The draw, the tally, and the history all happen on your device, and closing the tab discards the session. That is a deliberate constraint on every Sumvia site, and here it has a pleasant side effect: there is nothing for us to log about your decisions, because the decisions never reach us.

What it is not

It is not a certified randomness source. It is fair enough to decide who kicks off and who does the dishes; it is not audited, not certified for wagering, and produces no record anyone else can verify after the fact. If a decision needs to be provable to a third party later, you need a documented procedure with an audit trail, which a web page cannot give you.

Get in touch

Think a result is wrong, or found a bug? See the contact page. Reports that the coin is behaving oddly are especially welcome — they are the ones worth chasing down.