Fair dice without the dice
Lost the dice for a board game, or need a d20 for a role-playing session? This roller simulates any number of dice, from a single coin-like d2 up to a hundred percentile dice, and shows each die and the total. Results come from crypto.getRandomValues, your browser's cryptographically secure random generator, and use rejection sampling: random numbers that would make some faces slightly more likely than others are thrown away and drawn again, so every face has exactly the same probability. Many simple online dice use a quick “random × sides” calculation that is good enough, but this method is exactly fair.
Dice notation
Tabletop games describe rolls like 3d6+2: roll three six-sided dice and add two. Set the number of dice to 3, sides to d6 and the modifier to 2, and the result line shows the same notation with every individual die. Common types are d4, d6, d8, d10, d12 and d20 from Dungeons & Dragons sets, and d100 for percentage rolls. Six-sided dice are drawn with die faces, the others as numbers.
What to expect from the totals
A single die is equally likely to land on any face, but totals of several dice are not: with two d6, a 7 is six times as likely as a 2 or a 12, because more combinations add up to 7. The average of one d6 is 3.5 and of 2d6 is 7. Short runs often look streaky; that is normal randomness, not a fault.
Heads or tails
The coin flip uses the same fair generator with two outcomes. The page counts heads and tails, shows the percentage of heads and your current streak. Over a few flips the split will often be uneven; over hundreds of flips it settles close to 50%. Streaks of five or six in a row are more common than most people expect. Each flip is independent: a run of tails does not make heads “due”.