Flip a Coin — a fair 50/50 heads or tails online

Yes. It uses the browser's built-in cryptographic random number generator (crypto.getRandomValues) to pick heads or tails with exactly 1/2 each. Interestingly, real coins aren't quite 50/50. In 2007 Diaconis and colleagues at Stanford found that a hand-flipped coin lands on the side that was facing up before the toss about 51% of the time, and in a 2023 experiment where 48 people flipped coins 350,757 times, the starting side came up 50.8% of the time. It happens because a spinning coin wobbles around its axis.

No. The result is decided by a cryptographic random number the moment you press the button, and the 3D scene only shows the dice landing on it. Before the roll, the physics runs to the end without drawing anything; then one of the die's symmetries (a rotation that lays the shape exactly on top of itself) is chosen so that the chosen number sits on the face that ends up pointing up, and the die is drawn that way from the very first frame. That's why numbers never change mid-roll and real layouts, such as opposite faces adding up to 7, stay intact. The physics isn't trusted with the result because small differences in weight or collision error between faces could skew it slightly.

No. Flip a fair coin 20 times and there's about a 77% chance of a run of four or more of the same side, and about 46% for five or more. People feel that an even mix of heads and tails looks "random", but real randomness produces streaks more often than we expect. Five heads in a row don't make tails more likely next time, either — every flip is exactly 50/50.

Read it as "number d sides". 2d6 is the sum of two six-sided dice, d20 is one twenty-sided die and d100 (d%) gives 1 to 100. Adding +3 or -2 adds to or subtracts from the total, and you can mix kinds, as in 3d6+1d4. kh3 keeps the highest three, kl1 keeps the lowest one and dl1 drops the lowest one. So 4d6kh3 is the D&D ability score roll, 2d20kh1 is advantage and 2d20kl1 is disadvantage. You can roll up to 100 dice at once, with up to 1,000 sides.

For the roll you just made: the chance of getting exactly that total, the chance of that total or higher, and the average. They're exact, worked out by counting every combination rather than estimated from samples. For example, 7 is the most common total on 2d6 at 6/36 ≈ 16.7%, while 12 is 1/36 ≈ 2.8%. If there are so many dice or sides that the combinations get out of hand, it skips the odds and shows only the possible range.

Yes. After a roll, tap the dice you want to keep; they're held with a lock mark, and the next roll leaves them alone and re-rolls only the rest. You can tap the die on the table or its result chip below. It's handy for Yacht-style games where you collect the faces you want from five dice. To release a die, tap it again or press "Release all". Changing the notation releases all dice.

Yes. Hold the Roll or Flip button, the board or the Space key and a power bar fills at the bottom of the board; the moment you let go, it throws with that power. About a second gives the strongest throw, a quick press a gentle one. A coin flies higher and flips more times in the air, and dice fly faster and higher and tumble longer. Power only changes how it falls: the result (heads or tails, the number on each die) is picked separately by crypto randomness, so the odds are exactly the same.

Only in this browser (localStorage); nothing is sent to a server. It keeps your last 500 coin results and last 30 dice rolls, along with the options written on the coin and your dice expression. It isn't shared with other devices or browsers, and disappears when you press "Clear history" or clear the browser's site data.