Fairness & transparency

The creator picks how much less an opponent may join with: 95%, 90%, 85% or 80% of their stake (95% by default). The opponent can put in anything from that minimum up to 100% of the creator's stake.

Each player's chance equals their share of the pot. Matching the full stake is a 50/50 flip; joining a $100k flip with $95k gives the joiner 48.7% and the creator 51.3%.

Technically: a random server seed is committed (only its SHA-256 hash is shown) when the flip is created. On join, a ticket is drawn uniformly from the pot's value with HMAC-SHA256(server seed, "coinflip:<seeds>:<round>"); the creator holds the first tickets and the joiner the rest. The seed is revealed right after.

Every value unit you add is one ticket, so your chance equals your contribution divided by the pot. Example: 100k + 300k → 25% and 75%.

Tickets are assigned in join order. Entries lock 5s before the draw. The client seed is the SHA-256 of every participant's seed. The winning ticket is drawn uniformly from the pot total using HMAC-SHA256 output with rejection sampling (no modulo bias). The animated reel only displays the result chosen on the server.

Coinflip: 5% of the combined pot. Jackpot: 10% of the pot. Buying in the marketplace has no fee; the cart buys items back at 100% of the day's price.

The fee is fixed when a round is created and shown before you join. It is only collected when a round settles; cancelled, expired or refunded rounds pay no fee. The fee never enters the winner-selection algorithm.

Minecraft items can't be split. The exact fee is computed in value units (100 = $1) and rounded down. DonutDuel then takes whole items, starting with the most valuable item that fits, without ever exceeding the exact fee.

If whole items can't cover the exact fee, the uncovered remainder stays with the winner and is recorded on the settlement as a “fee shortfall”. Every round shows the exact fee, what was collected and which items were taken. No items are ever created or destroyed.

Prices come from completed DonutSMP auction-house sales (official DonutSMP API): the median of recent sales. They are republished once every 24 hours, so the price you see won't change until the next scheduled update.

The same price is used to buy items in the marketplace, to value stakes, and to sell items back in the cart. Asking prices from listings are never used. Items without a current trusted price can't be bought or staked.

When you stake items or request a withdrawal, the items or balance are reserved atomically: they stay yours but can't be used elsewhere. Settlement moves them exactly once. Cancelling an open coinflip, an expired challenge, or a jackpot round where nobody else joined releases everything in full.

Each player's stake is valued with the reference prices at the moment it entered the round, so later price changes can't alter a round in progress.

Open any round from the game pages, your history, or a profile to see participants, items, values, the settlement and the fairness record. Use the verifier above to recompute the result from the revealed seed.

There are no house-versus-player games and no house or bot accounts in coinflips or jackpots. Moderators cannot choose or change a winner; they can only cancel rounds that haven't been drawn, which refunds everyone.