Checking every open Kalshi, Polymarket and Polymarket US event, all day
We do the math on thousands of markets, so you only see the trades that still profit after every fee.
Base is free, no card. ArbTrader never touches your money, and your exchange keys stay in your browser. See the live demo →
Three tools, one subscription
Sweeps every open Kalshi, Polymarket and Polymarket US event for bundles that pay out more than they cost, priced at the real order book after fees.
Useful for: finding arbitrage without checking thousands of markets yourself.
See live spreads →Screenshot any market in any app and drop it in. We research it across the web and give a chance for every outcome from that research, with the evidence and every source, plus whether there’s a real spread to take.
Useful for: doing your homework on a bet in a minute. Not financial advice.
Research a market →Every big Polymarket and Kalshi trade as it happens, with the odds now, what the top wallets hold, and a flag when one lands on a spread you can take.
Useful for: seeing where big money is moving, and when prices are about to shift.
Open the Whale Tracker →This week’s results
Every spread ArbTrader showed this week, as if $1,000 went into each one, against the average bettor with the same money.
Odds Checker · screenshot it, drop it in
Take a screenshot of any Kalshi, Polymarket or Polymarket US market, on your phone or computer, and drop it in. We find the market and research it across the web the way you would with an hour to spare: the latest news, injuries and lineups, form, stats, history and polls. You get a chance for every outcome worked out from that research, never copied from the market’s price, with the evidence for and against and every source. It also checks whether there’s a real spread. Not financial advice.
Screenshot checks, with no daily limit, are part of Pro and Quant. Anyone can paste a link instead: three free checks a day with no account, ten with a free account. It won’t tell you what to trade and it isn’t financial advice: it researches the event and tells you whether the thing in front of you is what it looks like. ArbTrader never holds your money and never places a trade without your confirmation.
Whale Tracker · Pro and Quant
Every big trade on Polymarket and Kalshi within about 30 seconds, with the odds each platform gives that outcome right now. Each wallet gets a smart-money score from its real place on Polymarket’s profit leaderboards, and unusual activity is flagged: a new wallet placing a big bet, a big bet on a long shot, one trade that is a large share of the market’s day. Filter by odds and by when it resolves, see what the top wallets hold, and copy a trade if you choose to, after the risks are spelled out.
New to arbitrage? Start here
That’s arbitrage: buy every possible outcome of an event for less than it pays out, and as long as every leg fills, whichever one wins pays you back more than you spent. These short videos explain the idea. ArbTrader does the finding, the fee math and the checking.
Videos are by their creators on YouTube, not by ArbTrader, and aren’t advice. Thumbnails come from YouTube; a video only loads when you press play. Hover to pause the row.
How it works
Start your trial and log in at arbtrader.co. There is nothing to download, and the scanner is already running, the feed is there the moment you arrive.
Add a Kalshi API key and your Polymarket wallet address to see your own profit & loss; on Quant, add a Kalshi or Polymarket US key with trading permission for order tickets. The private key is imported into your browser’s key store, where page code can sign with it but can’t read it back out, and it never reaches our servers.
Every opportunity shows the exact contracts, prices, size resting at those prices, fees taken out, and a direct link to each leg, so you can check it yourself before anything happens.
Pro: click through and place each leg yourself. Quant: open an order ticket for the Kalshi or Polymarket US legs, set the size, confirm, and each leg is signed in your browser and sent as a fill-or-kill limit order, thinnest book first. A leg that misses gets one more try at up to break-even, so a moving price is less likely to leave you holding one side. International Polymarket legs are always placed by you; Polymarket.com doesn’t accept orders from other websites.
Why the list is short: the four checks every spread passes first →
Pricing
Base is free and shows you every spread the moment it appears. Pro adds the legs, prices and links you need to take one, your P&L, Odds Checker for spreads you found elsewhere, and the Whale Tracker. Quant adds alerts, the cross-platform pairs you can only get by combining venues, and an order ticket for Kalshi and Polymarket US.
Base
freeFree for as long as you want it. No trial to run out.
See every qualifying spread the moment the scanner finds it.
Pro
3-day free trialBilled monthly. 3-day free trial, cancel anytime.
Everything in Base, unlocked: the legs you need to take a spread, your P&L, and Odds Checker.
Quant
recommendedBilled monthly. 1-day free trial, cancel anytime.
Everything in Pro, plus alerts, more kinds of spread, and one-tap Kalshi and Polymarket US tickets.
How billing works: card required at checkout; you won’t be charged during the free trial (3 days on Pro, 1 day on Quant). If you don’t cancel before it ends, your plan renews monthly at the price shown, plus any sales tax (shown at checkout before you pay), until you cancel. No setup fees and no other ArbTrader charges, exchange trading fees are charged by the exchanges, not us. Switch plans or cancel anytime from your account page; see the refund policy. Refer a friend: they get 50% off their first paid month, and you get 50% off a month when they subscribe. Your exchange keys stay in your browser and your funds stay on the exchange; neither ever touches our servers.
FAQ
An arbitrage scanner for prediction markets that runs on the web. Log in at arbtrader.co and your dashboard checks every open Kalshi, Polymarket and Polymarket US event for bundles that pay more than they cost after fees, and shows the legs, prices, size and links. Connect your accounts and it also draws your profit & loss, computed in your browser, from your own trade history. Quant adds alerts, Kalshi ↔ Polymarket pairs you confirm, and Kalshi and Polymarket US order tickets you confirm.
All three run the same one-winner bundle scanner across every open Kalshi, Polymarket and Polymarket US event. Base is free and shows you each spread as it appears, with its return and how long it has left, but not the legs, prices, sizes or links; you can watch the scanner work, you just can’t act on it. Pro ($19.99/month) unlocks all of that plus your P&L, and you place the trades yourself. Quant ($24.99/month) adds email and Discord alerts, Kalshi ↔ Polymarket pairs you confirm, and one-tap Kalshi and Polymarket US order tickets. International Polymarket legs are placed by you on every plan.
It never opens a trade on its own. On Base and Pro, no; they report opportunities and Pro links you to each leg, and you place every trade by hand. On Quant it can send Kalshi and Polymarket US orders, but only when you open the ticket for a specific opportunity, set the size, let it re-check the live prices, and confirm; each leg goes out as a fill-or-kill limit order at the price you approved. The one exception is one you switch on yourself: Auto-sell, which you can arm on a position you already hold so it sells that position once you’d be ahead by the amount you set. It sells while your dashboard is open; when it’s closed, we email you the moment the target is hit so you can sell with one tap. It never buys, fires once and then turns itself off. International Polymarket blocks orders placed from other websites, so those legs are always yours to place.
You do. Your Kalshi private key (and, for Quant tickets, your Polymarket US secret) is imported into your browser’s own key store as a non-extractable key: the dashboard can ask the browser to sign a request with it, but neither the page nor we can read the key back out, and it is never uploaded. Each request is signed in your browser and passed through arbtrader.co only because the exchanges’ APIs don’t accept calls from web pages; we forward the signed request and the exchange’s answer, and never see the key. International Polymarket needs only your public wallet address. We never hold your funds on any platform.
Just an ArbTrader account. The live feed works the moment you log in; it uses public market data, not your accounts. A Kalshi API key and your Polymarket wallet address are optional and only power your P&L; on Quant, a Kalshi or Polymarket US key with trading permission powers order tickets. Discord alerts need a webhook URL from a server you control. You add all of these on the Connections tab of your dashboard, and you can remove them with one click. Want to look around first? Try the live demo.
The dashboard re-prices every listed spread about once a minute and sweeps all open events in rolling passes, so it can lag the market. Order tickets re-read the live order book the moment before you confirm, and refuse the ticket if the price moved or the size isn't there. Real spreads are rare and close fast; a human confirmation is part of every order by design, and nothing guarantees a fill at the price you saw.
No. ArbTrader is software that surfaces pricing information across platforms and, on Pro, sends 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 Pro and Quant from Manage billing on your account page, or drop back to Base for free. It's a monthly subscription with no lock-in.