Polymarket Bots
Prediction market arbitrage bot
A Python bot that buys both sides on Polymarket when YES plus NO costs less than 1 dollar, then merges them on-chain.
This project is a bot system I built to catch price imbalances on the Polymarket prediction market. It runs on the Polygon network and is written in Python. I, Berke Özyaşar, designed and built it as a personal project.
The core idea
In Polymarket's binary markets, 1 YES share and 1 NO share can always be merged into 1 USDC.e, whatever the outcome. So when the best ask prices on both sides add up to less than 1 dollar, buying both sides together and merging the positions on-chain locks in the difference. This happens especially often in short-term 5- to 15-minute crypto “up or down” markets.
System components
- Market discovery: finding suitable markets and token IDs through the Gamma API
- Scanner: a module that reads the order books roughly every 2 seconds, calculates net profit after Polymarket fees and gas costs, and applies minimum spread and profit thresholds
- Executor: a module that sends signed orders to both legs almost simultaneously
- Merging: merging positions on-chain or holding them until resolution
- Second strategy: a “dump & hedge” strategy that buys one side after a sudden drop, hedges with the other side once the total cost reaches an acceptable level, and cuts the loss if time runs out
- Monitoring: Grafana dashboards
Technical approach and risks
The system uses the py-clob-client and web3.py libraries. One leg filling while the other does not, fees eating the spread, slippage and thin liquidity are real risks; that is why a kill switch, a retry mechanism for rate limits and very small test sizes are part of the system. This page is not investment advice.
For a detailed technical write-up, see the Polymarket arbitrage bot post. For similar work, see the trading bots and automation bots pages; my MetaTrader work is here.
