Best Free Prediction Market Arbitrage Tools (2026)

Free arbitrage tools exist, several are genuinely good, and the catch is rarely the one you expect. It is not usually that the free version is crippled. It is that most free tools hand you data or maths rather than a finished scanner, so you supply the missing piece yourself. This guide covers the ones that work without a card, what each actually gives you, and the two free tiers that look useful until you read what is in them.

Every price and venue count below was checked against the tool's own site, documentation or repository in August 2026. Where a free tier excludes the feature you actually came for, that is stated rather than glossed over, because that is the most common way one of these lists wastes your afternoon.

The Free Tools at a Glance

Venue counts are what each tool documents itself, not what its marketing claims.

1. Predictefy: The Widest Free Coverage

Predictefy's arbitrage aggregator is free to use and spans more than fifteen venues, which is the part that matters on a list like this, because every other free option here stops at seven or fewer.

Coverage is not a vanity number in arbitrage. The gaps between Polymarket and Kalshi are the most heavily watched on the board and therefore the thinnest. The wider spreads sit on smaller venues like Opinion, Limitless, Predict.fun, Myriad and SX Bet, and a scanner that cannot see those never tells you they existed. Going from two venues to fifteen changes how many opportunities appear far more than any improvement in alert speed.

The matching is the part worth scrutinising, on any tool including this one. Predictefy maps differently worded contracts to the same underlying event, then checks deadlines and resolution rules before treating two markets as equivalent. That last step is what separates a usable signal from a trap, because two markets that sound identical but settle on different criteria are not an arbitrage. They are two unrelated bets that happen to look similar, and that is how people lose money on this.

Prices come from the best executable bid and ask on each venue's live order book rather than the last traded price, which matters because last-traded can be hours stale on a thin market and will show you a spread that is not really there.

What is paid: a Pro subscription unlocks more advanced arbitrage. The aggregator itself, which is what most people on this page are looking for, costs nothing.

2. Prediction Hunt: Best Free Alternative

Prediction Hunt runs an arbitrage scanner in the browser across seven platforms per its own documentation, with no login wall, no trial and no card. You can be looking at live cross-venue gaps about thirty seconds from now.

The seven are Polymarket, Polymarket US, Kalshi, PredictIt, ProphetX, Opinion and Predict.fun. Worth reading twice, because it includes venues most tools ignore entirely. PredictIt and ProphetX rarely appear in these lists.

Its marketing says six platforms while its documentation counts seven, the difference being whether Polymarket and Polymarket US are treated as one venue or two. They are separate exchanges with separate order books, so seven is the honest count.

The free part is the browser tool. A separate API has a free tier of a thousand requests a month and paid plans from forty-nine dollars, but you never touch that unless you are building something.

3. PolyRouter: Seven Venues Behind One Key

PolyRouter puts Kalshi, Polymarket, Manifold, Limitless, SX Bet, Novig and ProphetX behind a single API key with one normalised schema. It is free in open beta, rate limited to a hundred requests a minute, with no paid tier published at all yet.

That last part cuts both ways. Nothing to pay today, and no guarantee about tomorrow, so do not build something you cannot move.

One caveat decides whether it is useful to you: seven venues are documented, but full order book data is available on four. Arbitrage lives on the book, not the headline price, because a five percent gap with forty dollars of depth behind it is not a five percent opportunity. Treat it as four venues for arbitrage and the rest as context.

4. EdgeHunt: The Maths, Once You Have the Data

EdgeHunt is a free MIT-licensed Python package that does the arbitrage, expected value and Kelly sizing calculations locally. Know what it is before you install it, because other roundups describe it as a live Kalshi and Polymarket scanner and it is not one.

It ships no venue connections. There is no Kalshi or Polymarket module in the source, live adapters for both sit unticked on its own roadmap, and its data interface raises a not-implemented error until you supply a fetcher. It includes a synthetic feed for offline demos, and the README says so plainly: no network, no API keys, no account. Kalshi and Polymarket appear as fee models, meaning it knows what each venue charges so it can price an edge correctly, not that it can read their books.

Paired with a venue API you already call, or with PolyRouter, it is genuinely useful and the maths is tested and auditable. On its own it will not find you anything.

5. Calculators and Alert Channels

Two lighter categories worth knowing about.

Eventarb is a free multi-platform arbitrage calculator covering Kalshi and Polymarket, with cross-platform alerting. A calculator is not a scanner: you bring the two prices, it tells you whether the pair clears a dollar after costs. Useful while you are still learning what a real gap looks like.

Telegram alert channels are the free option nobody lists. Several push cross-venue signals at no cost, and coverage across Polymarket, Kalshi and Limitless is common. The tradeoff is control: you see what the operator decides to flag, on their schedule, with no way to filter by venue, size or spread. Fine as a second pair of eyes, poor as your only source, and worth watching for a week before acting on anything from one.

6. Two Free Tiers That Do Not Do Arbitrage

These appear on free lists constantly and both will waste your time if you sign up expecting a scanner.

Oddpool's free tier gives cross-venue search, event dashboards and a thousand API calls a month. The arbitrage scanner sits on the Pro tier at thirty dollars a month. The free tier is a genuine product and a fair way to see whether you like the interface, but the feature you came for is not in it.

Adjacent's free tier gives a public REST API and an MCP server, which is unusual and useful if you want an AI agent querying prediction market data. The data is delayed fifteen minutes. For indices, research or agent work that is fine. For arbitrage it is worthless, because any gap visible on a fifteen minute delay closed long before you saw it.

7. Your Own Spreadsheet, and Just Looking

Both major venues publish public APIs. A spreadsheet pulling prices for a handful of markets you already follow costs nothing, forces you to learn the fee maths properly, and has no monthly bill. The ceiling is low and it will never beat anyone to a gap, but the understanding transfers to every tool above it.

Below that, two browser tabs. Open the same event on two venues and compare. Slow, and you will not win a race with it, but it is the fastest way to learn what an equivalent market actually looks like, which is the skill all of this automates.

What Free Actually Costs You

The pattern across most of the list is that free tools give you a component, not a system. Predictefy and Prediction Hunt are the exceptions, in that both scan out of the box. Everything else hands you data, or maths, or an alert, and you assemble the rest.

That is a real cost, just not a cash one. Building a scanner on a raw API is a weekend if you write code and impossible if you do not. Running EdgeHunt means you already solved the data problem somewhere else. Telegram alerts mean accepting someone else's judgement about what counts as an opportunity.

The second cost is coverage. Free tools cluster around Polymarket and Kalshi because those APIs are the easiest to integrate, and those two venues are where every other trader is already looking. The wider gaps sit on smaller books, which is exactly where free coverage thins out.

When Paying Starts to Make Sense

Start free, and there is enough here that free goes a long way. There is no argument for paying before you can read a spread, confirm that two markets resolve on identical criteria, and work out what fees do to a thin gap.

Paying becomes rational at one of two points. Either you are consistently finding gaps and losing them to execution speed, or you have worked out that the venues you can see are too crowded to be worth trading. Both are problems that more advanced tooling addresses, which is what Pro subscriptions across this category exist for. The full comparison of what the paid tiers add is in our guide to the best prediction market arbitrage tools.

Conclusion

Free is a real option in this category, which is not true of most trading tooling. Predictefy's aggregator covers more than fifteen venues at no cost, Prediction Hunt covers seven in the browser, PolyRouter gives you an API while its beta lasts, and EdgeHunt is MIT licensed and will stay that way. Start there, learn what a genuine gap looks like and what fees do to it, and only consider a paid tier once you know which venues you actually want watched. Our guide to how prediction market arbitrage works covers the mechanics, and the arbitrage maths walks through the numbers step by step.