Wiki
Guides and references for trading prediction markets - the fees, rebates and mechanics that actually cost you money, explained with the real numbers.
Prediction market fees and rebates
What a trade actually costs on Polymarket, Kalshi, Gemini, Robinhood and more, with a calculator for the fee, the rebate and the effective price you pay.
Polymarket volume and fees, by category
Daily volume, open interest and the busiest categories on Polymarket, each with the taker fee and maker rebate that actually applies.
Kalshi volume and fees, by category
24h volume, open interest and the busiest categories on the regulated US exchange, each with the taker fee that applies.
The prediction markets directory
Every venue worth trading, the data you can backtest on, and the tools people have shipped. Rebuilt from an open repo every day.