Guide

Finding arbitrage opportunities on Polymarket

Arbitrage on Polymarket exploits price discrepancies between related markets. This guide covers logic arbitrage, cross-market arbitrage, detection methods, and risk considerations.

What this guide covers

Logic arbitrage: exploiting price inconsistencies within a single market
Cross-market arbitrage: exploiting discrepancies between related markets
Detection requires real-time monitoring of multiple markets simultaneously
Risk considerations include execution speed, liquidity, and market maker reaction

What arbitrage looks like on Polymarket

Arbitrage on Polymarket exploits situations where the prices of related markets or tokens are inconsistent. If the Up and Down tokens do not sum to approximately $1, there is an opportunity.

Logic arbitrage occurs within a single market. If Up ask is 0.40 and Down ask is 0.55, buying both costs 0.95 and pays out $1 on resolution: a guaranteed profit.

Cross-market arbitrage occurs between related markets. If BTC 5-minute markets on two different platforms have different prices, you can profit from the difference.

Arbitrage opportunities are rare and fleeting on Polymarket because market makers actively monitor prices and adjust quotes.

Logic arbitrage detection

For a binary market, the sum of Up and Down token prices should be approximately $1 (minus the spread). If the sum deviates significantly, there is a logic arbitrage opportunity.

Compute the combined cost of buying both outcomes: best_ask_up + best_ask_down. If this is less than $1, buying both guarantees a profit of $1 - combined_cost on resolution.

Monitor the sum continuously. When it drops below $1 (minus a threshold for transaction costs), trigger a buy signal for both tokens.

The challenge is execution speed. By the time you detect the discrepancy and place orders, the prices may have moved. Automated detection is essential.

Cross-market arbitrage

Cross-market arbitrage exploits price differences between markets on different platforms or markets with overlapping outcomes.

On Polymarket specifically, cross-market arbitrage can occur between markets with correlated underlying assets. If BTC and ETH markets are mispriced relative to each other, there may be a relative value opportunity.

Detect cross-market arbitrage by maintaining real-time price feeds for all related markets. Compare prices at each timestamp and flag deviations.

Cross-market arbitrage requires capital on multiple platforms and the ability to execute simultaneously on both. This introduces operational risk.

Risk considerations

Execution risk: the price may move between detection and execution. Automated systems with low latency are essential.

Liquidity risk: the arbitrage may require buying or selling size that exceeds available depth. Walking the book may eliminate the profit.

Market maker reaction: market makers adjust quotes in response to order flow. Your arbitrage trade may cause the market to move against you.

Counterparty risk: on centralized platforms, there is a risk of order rejection or platform issues.

Code examples

def check_arbitrage(books, threshold=0.01):
    opportunities = []
    for snap in books:
        if not snap["asks"] or not snap["bids"]:
            continue
        up_ask = snap["asks"][0]["price"]
        down_ask = 1 - snap["bids"][0]["price"]
        combined = up_ask + down_ask
        if combined < 1.0 - threshold:
            opportunities.append({
                "timestamp": snap["timestamp"],
                "up_ask": up_ask,
                "down_ask": down_ask,
                "profit": 1.0 - combined,
            })
    return opportunities

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FAQ

Is arbitrage common on Polymarket?

Logic arbitrage is rare because market makers actively monitor quotes. Cross-market arbitrage between platforms is more common but requires multi-platform access.

Can I automate arbitrage detection?

Yes. Monitor the sum of Up and Down ask prices in real-time. When it drops below $1 minus your threshold, trigger a buy signal for both outcomes.

What profit should I expect from arbitrage?

Logic arbitrage on Polymarket typically yields 0.5 to 2 cents per trade before transaction costs. Volume and speed matter more than per-trade profit.

What are the main risks?

Execution risk, liquidity risk, market maker reaction, and counterparty risk. Automated systems with low latency help mitigate execution risk.