ArbBets vs Rainmaker

What ArbBets does

Arbitrage scanner and data feed for prediction markets and sportsbooks. The Pro plan scans Polymarket, Kalshi and Opinion for the same event priced differently, shows the spread after Kalshi's fees with order-book sizing and links to both legs, and adds a value-bet finder, a weather-market tool that compares National Weather Service forecasts with market prices, a “sharp money” scanner and funding-rate spreads between perpetual-futures exchanges. You place the trades yourself. The top plan sells the same opportunities as a REST API for your own bot, plus a self-hosted Polymarket market-making agent. Plans are $59, $149 and $299 a month; the cheapest covers sportsbook arbitrage only.

• Cross-venue scanner of the same event on Polymarket, Kalshi and Opinion, with the spread after Kalshi's taker fee
• Order-book sizing: enter a budget and get the contract count for each leg
• Positive-EV finder, odds screener, Sharp Money Scanner and Weather Edge Finder for Kalshi and Polymarket weather markets
• Funding-rate spreads between perpetual-futures exchanges for delta-neutral trades
• REST API on Premium with full order books and pre-computed spreads, with Python examples

• A tool box for people who place both legs themselves, or who want to build their own bot on its data. The prediction-market scanner starts on the $149 Pro plan — the $59 Basic plan is sportsbook arbitrage only — and the API that would let a bot act on it is $299 a month.
• Its own research is the useful reality check. A report dated August 2026 took six snapshots of the scanner from December 2025 to August 2026 and found 241 profitable Kalshi–Polymarket pairs among 3,030 matched markets, with a median return after fees of 2.1% and 91% of them under 5%; the higher figures it lists are mostly long-dated markets with capital locked for months. The home page's “100+ opportunities daily” and “2–8% spreads” sit above that median, and its Fed-decision card is an illustration. The free “live” preview on the Kalshi–Polymarket page is labelled a delayed sample and was last updated on Jun 19, 2026 when we looked on Nov 2.
• Matching is the risk in cross-venue arbitrage. One of the report's own examples, an 11.1% gap on whether Barack Obama would be named in Epstein files released in 2026, is the kind of pair where the two venues' resolution wording deserves a careful read before you buy both sides. ArbBets holds no funds or keys for the scanner; the market-making agent runs on your own server.