Polymarket + Kalshi Arbitrage Finder: what it does, what it costs, where it stops

What it does

Each run scans both venues, scores candidate pairs from 0 to 1 on keyword similarity, and flags anything under 0.4 as a loose match that needs manual verification before trading.

Output rows carry the spread percentage, profit percentage, trade direction, prices on both venues, cost and profit per unit, the similarity score, market close dates and direct market URLs.

• Inputs: minSpread (default 0.02), minReturnPct (0.5%), minSimilarity (0.25), minLiquidity (0), minVolume24h (0), maxResults (500)
• Matches scored 0 to 1; under 0.4 flagged as loose
• 100% run success rate shown on the listing when checked

Pricing

The listing states the Actor is paid per event and usage: a fixed $0.05 per Actor start plus Apify platform compute. Apify's own free plan covers a small amount of compute, so light scheduled use can be near zero, but the Actor start fee always applies.

Venues and data

Polymarket and Kalshi only. The listing points to a related Actor by the same author for PredictIt. It notes Kalshi is US-regulated by the CFTC and that Polymarket serves non-US users, which matters if you plan to trade both legs from one jurisdiction.

Liquidity and 24-hour volume filters default to zero, so a first run will include thin markets where the displayed gap cannot be filled at size. Raise minLiquidity before trusting the top rows.

Where it falls short

Keyword matching is the weak point. Two markets with similar titles can have different resolution sources or dates, and the tool itself asks you to verify any match below 0.4.

The listing's disclaimer is blunt: real arbitrage requires both trades to fill at once, and slippage, fees and timing can erase the profit. Fees are not netted in the output.

Who should use it

Traders who already use Apify or want a scheduled scan piped into Sheets, Slack or a webhook. If you want a live screen, ArbiTrack or the Prediction Hunt arb page is simpler.