The same market, priced two ways

Prediction market arbitrage, explained

What is prediction market arbitrage?

When the same event trades on more than one venue (Polymarket, Kalshi/Robinhood, PredictIt), the YES price on one venue and the NO price on another can add up to less than $1. Buying both locks a guaranteed $1 payout for less than $1, and the difference is the arbitrage.

Is there a Polymarket vs Kalshi arbitrage API?

Yes. This board is a free JSON API at /api/v1/arbitrage and an MCP tool (get_arbitrage), so bots and agents can poll live Polymarket, Kalshi and PredictIt arbitrage opportunities without scraping each venue.

Which venues are covered?

Polymarket, Kalshi (and Robinhood, which trades on Kalshi's exchange), and PredictIt. Every market is normalized to a single YES/NO price and matched to the same real-world event across venues.

Is it free, and is this financial advice?

The board and the API are free, no signup. This is an informational feed, not financial advice. Live arbitrages are often fleeting, and fees, KYC, gas and withdrawal limits eat into the spread, so verify each market's resolution rules and costs before trading.

What are the types of Polymarket arbitrage?

Two main kinds. Internal (bundle) arbitrage is buying YES and NO inside a single Polymarket market when they sum to under $1 (for example YES at 60¢ and NO at 38¢ totals 98¢, a locked 2¢). Cross-platform arbitrage is the same real-world event priced differently across venues: buy the cheap YES on one and the cheap NO on another (Polymarket vs Kalshi/Robinhood or PredictIt). This board scans the cross-platform kind live.

Is arbitrage allowed on Polymarket?

Yes. Buying mispriced YES/NO shares is ordinary market activity, not against Polymarket's rules. The real constraints are practical: order-book depth is thin at the mispriced level, so large size is hard to fill, and Polymarket restricts some jurisdictions (including the US), so check your own eligibility.

Is Polymarket arbitrage profitable?

Spreads are usually small (often 1-5%) and short-lived. High-frequency bots capture the obvious ones in milliseconds, and gas, fees, and slight differences in how each venue resolves an event can erase a thin edge. It can be profitable on real, verified mismatches with fast execution, which is exactly what this scanner surfaces, but it is not free money.

Is there a Polymarket arbitrage scanner or bot?

This page is a live Polymarket, Kalshi and PredictIt arbitrage scanner, refreshed every 30 minutes. For a bot, point it at the free JSON API (/api/v1/arbitrage) or the get_arbitrage MCP tool: both return the same matched pairs and live prices, so an agent can poll opportunities and act without scraping each venue.

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