Prediction Market Aggregator

Aggregators fall into two broad categories. Trading aggregators focus on Contract Price comparison: they query the Order Book of Kalshi, Polymarket, and other exchanges to display the best available price for each side of an event contract. This supports Line Shopping — choosing the platform where the same outcome is priced most favorably. Forecasting aggregators take a different approach, collecting probability estimates from forecasters on platforms like Metaculus and Manifold and computing ensemble forecasts to improve accuracy. The AGI Timelines Dashboard is an example, aggregating estimates from Metaculus, Manifold, Kalshi, and other sources. Some tools combine both functions, displaying prices while also synthesizing Wisdom of the Crowd signals.

When the same event is listed on both Kalshi and Polymarket, prices can diverge due to differences in trader composition, Liquidity, and fee structures. An aggregator that monitors both platforms can surface situations where the YES price on one venue plus the NO price on the other totals less than $1 — a theoretically riskless Arbitrage profit. In practice, Slippage, Trading Fees, withdrawal delays, and the complexity of moving USDC Collateral versus dollars between platforms eat into these margins. Nevertheless, aggregators accelerate Information Aggregation across venues, driving prices toward consensus and improving overall Market Efficiency. Algorithmic traders use Trading API connections through aggregator SDKs to execute cross-platform strategies automatically.

By mid-2026, several aggregator services had established significant user bases. Prediction Hunt offers a REST API with a single authentication key spanning Polymarket, Kalshi, PredictIt, and ProphetX, plus a web interface for manual comparison. The open-source PMXT SDK normalizes order submission and market data across multiple platforms in Python and TypeScript. Third-party analytics sites like Polymark.et catalog individual platform tools, leaderboards, and aggregator products. Metaculus serves as a community forecasting aggregator, publishing calibrated probability distributions on long-horizon questions alongside live Polymarket and Kalshi prices for the same events. These tools collectively reduce the friction of the fragmented prediction market landscape by providing unified views of global event probabilities.