Prediction-market & sportsbook spread scanner
ArbTrader watches Kalshi, Polymarket, and sportsbook moneylines around the clock for same-market, cross-platform, and cross-bookmaker spreads — over real-time feeds when available — and lays out the exact legs, prices, and links so you can act on them.
Self-hosted, from $15/month. Runs on your machine, with your own API keys — never ours.
How it works
Run ArbTrader on your own machine and add your Kalshi and Polymarket API keys. They stay local — we never see them.
Same-market, cross-platform, and cross-bookmaker spreads populate as they're detected — over real-time WebSocket feeds when available, with an optional Discord ping the instant one clears your threshold.
Every opportunity shows the exact contracts, prices, sizes, and a direct link to each leg, so you can check it before anything happens.
Base: click through and place each leg yourself. Pro: open an order ticket on a Kalshi/Polymarket spread, set the size, confirm, and both legs go out from your machine. Nothing is ever sent without your confirmation, and sportsbook bets are always placed by you.
What it detects
One platform, one market: every outcome summed costs less than $1. This is arbitrage by construction — same contract, same resolution rules, no judgment call involved.
A Kalshi market and a Polymarket market that look like the same real-world event. ArbTrader surfaces title-similarity matches for you to inspect and confirm before they're tradable.
One game, two sportsbooks: the cheapest price on one team from one book plus the cheapest price on the other team from a different book costs less than $1 combined. Same game, same clock — just priced differently by different bookmakers.
Before you pay for this
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.
Pricing
Base finds the spreads and tells you about them. Pro adds an order ticket, so acting on a Kalshi or Polymarket spread is a size, a checkbox, and one click.
Base
3-day free trialAlerts and links. You place every trade yourself.
Pro
3-day free trialEverything in Base, plus one-tap order tickets.
3 days free, then billed monthly via Stripe. Switch plans or cancel anytime from Manage billing. Both plans run entirely on your own machine — your API keys and funds never touch our servers.
FAQ
A spread scanner for prediction markets and sportsbooks. It watches Kalshi, Polymarket, and sportsbook moneylines for same-market, cross-platform, and cross-bookmaker spreads and shows you the exact opportunity — the legs, the prices, the links — the moment it finds one, with optional Discord alerts so you don't have to watch the dashboard.
Both plans scan the same markets, send the same alerts, and run on your own machine. Base ($15/month) stops at the alert: you get the legs, prices, and a link to each one, and you place the trades yourself. Pro ($45/month) adds an order ticket to every Kalshi and Polymarket opportunity — pick a size, confirm, and ArbTrader submits both legs for you from your machine. Sportsbook opportunities work the same on both plans: you place those bets yourself.
Never on its own. On Base, no — it reports opportunities and links you to each leg, and you place every trade by hand. On Pro, ArbTrader can submit Kalshi and Polymarket orders, but only when you open the ticket for a specific opportunity, set the size, tick the confirmation, and press Submit. There's no auto-trade setting. Sportsbook bets are never placed by ArbTrader on either plan — sportsbooks don't offer a betting API, and most prohibit automated wagering.
No. ArbTrader is self-hosted: you run it on your own computer or server, and your Kalshi API key and Polymarket wallet key stay there. We never receive, store, or have access to either. That's true on Pro too: the trading-enabled keys Pro uses stay on your machine, and orders go straight from your computer to the exchange.
None to start — ArbTrader runs against bundled sample data with zero accounts or keys, including a sample sportsbook example, just to see how it works. To see real prices you'll want a Kalshi account and/or a Polymarket wallet address, and a free API key from The Odds API for sportsbook lines. Discord alerts need a webhook URL from a Discord server you control. Every one of these is optional and independent of the others.
Kalshi and Polymarket order books stream over WebSocket when configured, which is sub-second — well beyond what polling can do. Sportsbook odds refresh on a slower, credit-budgeted schedule (see the setup docs). Either way, ArbTrader gets you the information fast. On Base, placing the trade is a manual step you do yourself; on Pro, confirming a ticket sends both legs right away — but a human confirmation is part of every order by design, and no plan guarantees a fill at the price you saw.
No. ArbTrader is software that surfaces pricing information across platforms and, on Pro, submits orders you've reviewed and confirmed. Whether to trade, and how much, is always your decision and your risk.
Yes, anytime, including during the trial — you won't be charged unless you're still subscribed when it ends. Switch between Base and Pro from Manage billing on your account page. It's a monthly license with no lock-in.