The spread scanner for prediction markets.

Before you pay for this

What you're actually buying

• ArbTrader never trades on its own, on either plan. On Base it's a reporting tool: it shows you the legs, prices, and a link to each one, and you place every trade by hand. On Pro it can submit Kalshi and Polymarket US orders, but only after you open the ticket for that specific opportunity, set the size, and confirm it. There is no auto-trade mode. International Polymarket legs and sportsbook bets are always placed by you.
• Sending every leg is not the same as locking in the spread. Each leg is its own order — a bundle can have many legs, and they don't fill as one transaction. A ticket sends the legs one at a time and stops the moment one doesn't fill, which leaves you holding the ones that did — it tells you exactly what you're holding, but unwinding it is yours to do. If a price moves first, one leg can fill while the other doesn't, leaving you with an unhedged position until you close or complete it yourself. ArbTrader doesn't unwind it for you.
• Pro order tickets need a Kalshi or Polymarket US key that can trade. That key lives in your browser's key store on the computer you added it on. Anyone who can use that browser profile could place orders with it — lock your computer, disconnect the key when you're done on a shared machine, and use a read-only key if you only want P&L. Requests are signed in your browser and relayed through arbtrader.co, which never sees the key itself. Polymarket US hasn’t published rules specifically about third-party tools placing orders with a customer’s own key; check their terms before you rely on it.
• Genuine, capturable arbitrage on Kalshi and Polymarket is rare and closes fast. These are liquid markets watched by other bots running similar scans; a spread you see may already be thinner or gone by the time you act. Alerts and Pro's order tickets shrink the time between a spread appearing and your orders going out — they don't guarantee a fill at the price you saw.
• Cross-platform and cross-bookmaker matching is only as good as what you personally confirm. A Kalshi-to-Polymarket pairing you haven't verified, or a sportsbook line that's already moved, can turn a "hedge" into an unhedged position. Unconfirmed matches are always shown separately and flagged as needing review — never treated as high-confidence.
• A bundle is only a hedge if exactly one listed outcome wins. We only list events where the platform’s own data says so, but a platform can clarify or change an event’s rules — read them before you trade.
• The sportsbook and order-ticket integrations are built from each platform's own published API documentation, not verified against our own funded live account (we don't run one, and never see yours). Spot-check them against the platform's own numbers the first time you use each.
• Fees and size are estimates at the moment we checked. Bundle spreads use Kalshi’s published fee formula and each Polymarket market’s own fee settings, at the size resting at the best price — your fills can differ, and rules or fees can change. Cross-platform pairs use the same exact fee rules; sportsbook lines carry the book's margin inside the price. Capital sits tied up until the event resolves, so judge a spread by its return over that time, not the raw number.
• Legality and tax treatment of prediction-market trading and sports betting vary by state and country and change often. Confirm you're eligible to use each platform or sportsbook from your location, and that its terms allow API-based trading on your account, before connecting a real one.

Nothing on this page is financial, legal, or betting advice. Past spread detection does not guarantee future opportunities, and trading and betting both involve risk of loss — including total loss of amounts wagered or traded.