Questions
Prediction market arbitrage: frequently asked questions
Spreads, fees, depth and resolution risk — the short version.
What is prediction market arbitrage?
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The same event often trades at different prices on different venues. If YES costs 41¢ on one venue and NO costs 55¢ on another, buying both costs 96¢ and exactly one side pays $1 — a 4.2% return if both markets resolve the same way.
How is profit calculated?
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Profit = (number of YES+NO pairs) × $1 − what you paid, including each venue's taker fees. ROI is profit divided by capital. APR annualizes ROI by how many days your money stays locked until the later market resolves.
What are the main risks?
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The main one: both markets must resolve the same way. Venues sometimes word rules differently, use different data sources or cut-off times. Always read both markets' rules. Also check order book depth — quoted prices may only cover a small size.
Why do some spreads show a tiny dollar profit?
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Profit is capped by the depth actually on the order book at the quoted price. A 20% spread with $5 of liquidity is worth $1. Use the Min depth filter to hide thin books.
What does match confidence mean?
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How closely the two markets' wording, dates, thresholds and outcomes agree. 90%+ matches are usually identical contracts; lower scores deserve a careful read of both rule sets.
Which venues are supported?
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Polymarket, Kalshi and Limitless today. More venues are added as their APIs and matching quality allow.
Is it free?
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Yes. ArbSonar is free to use. Some outbound links are partner links, which may earn us a commission at no cost to you.