Arbitrage scanner for prediction markets
ArbTrader checks every open Kalshi, Polymarket and Polymarket US event for bundles that pay out more than they cost, priced against the live order book, after each platform’s fees, and shows you the exact legs, prices, size and links. It all runs at arbtrader.co: nothing to install, and your P&L is read in your own browser with keys that never leave it. See what has to be true first →
Base is free, no card. Pro from $19.99/month at launch pricing. Runs in your browser, no download, no setup. Your exchange keys stay in your browser; we never receive them.
What 90 days would look like · real data
Not a backtest; there is no trading history to test against. This projects one real snapshot of the live feed forward, conservatively, next to what ordinary directional betting on these same venues actually returns, per public reporting.
Projection, not a result. This assumes you personally place every qualifying spread the scanner finds, every day, for 90 days, based on one real snapshot of today's feed. Nobody has run this for 90 days.
Simulated from one real, dated snapshot, cut for fees, variance and missed legs; not a past result or a guarantee. See how these numbers are derived →
Spread Verifier · free to try
You don’t have to switch tools to get a second opinion. Paste any Kalshi, Polymarket or Polymarket US event, from any source, and it goes through exactly the checks this scanner runs before anything reaches its own feed. Three checks a day are free and need no account.
Three free checks a day with no account, ten a day with a free account, and no daily limit on Pro and Max. It won’t tell you what to trade, and it isn’t advice; it tells you whether the thing in front of you is what it looks like.
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 Max, 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. Max: 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, one at a time. International Polymarket legs are always placed by you; Polymarket.com doesn’t accept orders from other websites.
Why the list is short
Exactly one listed outcome can win, or one bracket contains another. Thousands of events are skipped a sweep for failing this.
The live book, at the size actually resting there, net of each platform’s own fees.
One tap sends every leg as a signed, fill-or-kill order. Nothing sent until you confirm. Max.
Re-prices about once a minute; bots react in milliseconds. This isn’t a speed race.
What counts as a spread, and how this compares to a plain price screen →
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, and Spread Verifier for spreads you found elsewhere. Max 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 trialLaunch price for subscriptions started by Dec 31, 2026. New subscriptions after that are $30/mo.
Everything in Base, unlocked: the legs you need to take a spread, your P&L, and Spread Verifier.
Max
recommendedLaunch price for subscriptions started by Dec 31, 2026. New subscriptions after that are $45/mo. 3-day free trial.
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 3-day trial. 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. Max 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 launch price, $30 after Dec 31, 2026) unlocks all of that plus your P&L, and you place the trades yourself. Max ($24.99/month launch price, $45 after Dec 31, 2026) 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.
Never 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 Max 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. There's no auto-trade setting, and each leg goes out as a fill-or-kill limit order at the price you approved. International Polymarket blocks orders placed from other websites, so those legs are always yours to place.
You do. Your Kalshi private key (and, for Max 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 Max, 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.
Not on raw speed, and we don’t claim to. Dedicated bots stream every order book and react in milliseconds; ArbTrader re-prices about once a minute and a person confirms every order. Where it earns its keep is the spreads bots tend to skip: cross-platform pairs that need a human to read both sets of rules, newer and quieter venues like Polymarket US, small sizes that aren’t worth a bot’s time, and spreads that tie money up for weeks. It also saves you hours of checking every event by hand.
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 Max from Manage billing on your account page, or drop back to Base for free. It's a monthly subscription with no lock-in.