PredictMarketCap is a prediction market data aggregator that compares real-time odds across Polymarket, Kalshi, Limitless, and Predict.fun. It ranks markets by volume, shows cross-platform price spreads, and helps you find where platforms disagree on the same event.
Prediction markets let traders buy and sell shares tied to real-world outcomes. Each share pays out $1 if the event happens. If a share trades at $0.60, the market is pricing a 60% probability. Prices move as traders buy and sell based on new information.
Polymarket is a crypto-native prediction market that trades in USDC on the Polygon blockchain. Kalshi is a CFTC-regulated exchange that accepts US bank deposits and is available to US residents. Limitless Exchange is a decentralized prediction market on the Base blockchain with zero trading fees. Predict.fun is an on-chain prediction market on BNB Smart Chain built on a Polymarket-style orderbook with USDT collateral. PredictMarketCap compares odds across all four platforms so you can see where they agree and disagree.
Arbitrage occurs when the same event has different prices on different platforms. For example, if Polymarket prices an outcome at 60% but Kalshi prices it at 55%, traders can potentially profit from the spread. PredictMarketCap highlights these cross-platform price differences.
Usually less than it looks. We audited 186 outcome pairs priced between 2¢ and 98¢ on both Polymarket and Kalshi: with both quotes fresh, the median gap was 0.78¢, and only 1.5% of pairs differed by 5 cents or more. Of the 12 largest headline gaps, none survived a staleness check — each had one side that had not traded recently, so the spread was an artifact of an old quote rather than a tradeable difference. Over six months we logged 385 sustained gaps of 2¢ or more, which is the honest size of the opportunity before fees.
The full audit, with its 385-episode dataset: Prediction Market Arbitrage, Measured
It depends on the individual market rather than the platform. Across 186 matched outcome pairs, the median difference between Polymarket and Kalshi on the same outcome was 0.78¢ once both quotes were fresh — close enough that neither venue is reliably better priced. The practical answer is to check the specific market you care about, which is what the cross-platform comparison pages are for.
Use a canonical event page. PredictMarketCap matches the same real-world question across Polymarket, Kalshi, Limitless, and Predict.fun and shows every venue's price side by side, so you can see the spread rather than opening four tabs. Matching is done per outcome, so "Yes" on one venue is compared against the equivalent outcome on the other rather than against a similarly-named market.
The busiest markets refresh about once a minute, so a live event moves on the page within roughly a minute of moving on the venue. The rest of the board refreshes on a slower cycle, and the homepage itself rebuilds every 15 minutes.
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