Polymarket Arbitrage: Where the Edge Actually Is

Polymarket runs on order books, and order books drift. When hundreds of markets move on news at once, mispricings appear faster than any human can act — which is exactly where a bot earns.

Complementary-outcome arbitrage

In a binary market, YES and NO should sum to 1. When the books briefly let you buy both sides for less than 1 (after fees), you lock a risk-free payout at resolution. These windows are small and fleeting — a bot scanning every book catches them; a person doesn't.

Cross-market relationships

Related markets should price consistently. "Candidate wins state X" and "Candidate wins the election" have a logical relationship; when one lags the other, there's an edge. Modeling these relationships across many markets is where systematic traders pull ahead.

Market making the spread

Beyond pure arbitrage, quoting two-sided liquidity on liquid markets earns the spread — with the same inventory and resolution-risk management a perp maker needs, plus one twist: as a market approaches resolution, you must widen and flatten, because the outcome is about to become certain.

Resolution is the real risk

The mistake that wipes out naive bots is holding into resolution on the wrong side. Resolution-aware exits — closing or hedging before an event resolves unless you want the exposure — are essential.

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See our Polymarket Arbitrage case study and Polymarket Spread Bot. We build these end to end — start a project.