Best Prediction Market Arbitrage Tools (2026)

The tools that actually work for prediction market arbitrage are cheaper and fewer than the category's marketing suggests. Three of the strongest cost nothing at all, the best paid options run between thirty and fifty dollars a month, and how many venues a scanner watches matters far more than how fast it alerts you. This guide covers the ten we could verify, and what each one will and will not do.

This guide ranks the prediction market arbitrage tools that we could confirm exist, operate, and do what they claim in 2026. Each entry was checked against the product's own site, its documentation, its repository where one exists, and its published pricing. Tools we could not corroborate outside a single promotional page were left out, and we say plainly which ones those were and why.

The Tools at a Glance

Pricing is what the vendor publishes as of August 2026. Venue counts are what each tool documents itself, not what its marketing claims.

1. Predictefy: Best for Cross-Venue Coverage

Predictefy scans more than fifteen venues, against the two that most tools on this list stop at, covering Polymarket and Kalshi alongside Opinion, Limitless, Predict.fun, Myriad, SX Bet, Gemini and others. That breadth is the single thing that most changes how many opportunities you actually see, because a scanner watching two venues is blind to the ones where pricing is loosest, and those tend to be the smaller books nobody else is quoting.

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 there.

Pricing and access: the arbitrage terminal starts at eighty-eight dollars a month. API and SDK access is priced separately and has not been released yet, so if you are building rather than trading by hand, that is a different conversation. Access to the arbitrage feed was invite-gated at the time of writing, meaning a code is needed before it unlocks.

2. Adjacent: Best for Indices and Agent Access

Adjacent indexes and benchmarks prediction markets and event contracts. The free tier gives a public REST API and an MCP server with fifteen minute delayed data, and Pro at fifty dollars a month adds realtime indices and reference rates. It documents Kalshi and Polymarket, though Polymarket returned no records on the public API when we checked, so treat Kalshi as the venue you can rely on today.

The MCP server is the unusual part and the reason it earns a place here: it lets an AI agent query prediction market data directly. If your workflow involves an agent doing the watching, this is currently one of the few tools built for that rather than retrofitted to it. The fifteen minute delay on the free tier makes it useless for live arbitrage, so price the Pro tier in from the start if that is your use case.

3. EdgeHunt: Best Fee and Edge Maths, If You Bring the Data

EdgeHunt is a free MIT-licensed Python package that does the arbitrage, expected value and Kelly sizing maths locally. It is worth knowing exactly what it is, because other roundups describe it as a live Kalshi and Polymarket scanner and it is not one.

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

That makes it genuinely useful for a specific job. If you already have market data, from a venue API you are calling yourself or from PolyRouter, EdgeHunt gives you tested, auditable maths for whether a spread survives fees and how much to stake. If you want something that finds opportunities on its own, this is not it, and installing it expecting a scanner will waste an afternoon.

4. PolyRouter: Widest Venue Coverage Behind One API

PolyRouter puts Kalshi, Polymarket, Manifold, Limitless, SX Bet, Novig and ProphetX behind a single API key with a normalised schema. That is the broadest venue list of any unified API we verified, and it includes several of the newer regulated exchanges most aggregators skip.

It is free in open beta, rate limited to a hundred requests a minute, with no paid tier published at all. Worth one caveat before you plan around the venue count: seven are documented, but full order book data is available on four of them, and arbitrage needs books rather than headline prices.

5. Marketlens: Best for Testing a Strategy Before Funding It

Marketlens sells tick-level historical Polymarket order book and trade data through a Python SDK, plus a backtesting API, at twenty-nine dollars a month on its Pro tier, with a free tier below it. It covers one venue.

It is on this list because it answers a question none of the scanners can: would this strategy have made money. A live scanner shows you gaps as they appear. Historical order book data lets you check whether those gaps were ever fillable at the size you intend to trade, which is the question that decides whether an apparent edge survives contact with reality.

6 and 7. The Free Routes: Your Own Spreadsheet, and Just Looking

Both venues publish public APIs. A spreadsheet pulling prices for a handful of markets you already follow costs nothing, teaches you the fee maths properly, and has no monthly bill attached. The ceiling is low and it will not catch anything fast, but the understanding transfers to every tool above.

Below that, two browser tabs. Open the same event on two venues and compare. It is slow and you will not beat anyone to a gap, but it costs nothing and it is the fastest way to learn what an equivalent market actually looks like, which is the skill the tools are automating.

How We Checked, and Why Some Tools Are Missing

Every entry above was checked against the product's own site, its documentation, its repository where one exists, and its published pricing. Several tools that appear in other roundups of this category are not here, for reasons worth stating rather than leaving as a silent omission.

Some are not commercial products. One widely listed name is a university hackathon submission with nothing to sign up for, and another describes itself in its own page markup as pre-order rather than released. Both are interesting, neither is something you can rely on this month. Others advertise automated execution that their own pricing pages do not yet offer, which is the single claim in this category most worth checking before you pay for it.

One structural thing is worth knowing when you compare roundups. Several of the highest-ranking guides for this term are published by companies that also sell a tool in them, ours included, and the ranking usually reflects that. Read the pricing page rather than the ranking, and note which tier a headline price actually refers to: at least one popular guide leads with a monthly figure that covers sportsbook arbitrage, while its prediction market scanning costs several times more.

How to Choose Between Them

Four things decide this, roughly in order of how much they matter.

Venue coverage. This dominates everything else. Two venues means you see the gaps between two venues, and the wider spreads usually sit on the smaller platforms. A slower scanner watching seven venues will show you more real opportunities than a fast one watching two.

Whether prices are executable. A tool quoting last traded price is showing you history. You want best bid and ask off the live book, with the size behind it, because a two percent spread on a market with forty dollars of depth is not a two percent opportunity.

Whether resolution rules are compared. The most expensive mistake in cross-venue arbitrage is two markets that read the same and settle differently. Ask any tool how it decides two markets are equivalent. If the answer is title matching, be careful.

Fees, and whether they are in the number. Most tools display gross spreads. Kalshi's fee structure alone can consume a thin gap entirely. If the tool does not subtract fees, you have to, every time, before the number means anything.

What None of These Tools Do

Every tool on this list finds opportunities. Not one of them reliably takes both sides of the trade for you, and the ones that advertise automated execution turned out, on inspection, to be either waitlisted or not shipped.

That matters more than it sounds, because the risk in this strategy is concentrated almost entirely in execution. One leg fills and the other moves. The displayed size evaporates as you click. Your capital sits locked on two venues until the event resolves, which can be months. A scanner solves the finding problem and leaves the hard part with you.

Treat every displayed spread as gross potential rather than profit, and size accordingly. None of this is financial, tax or legal advice.

Conclusion

The tools that survive scrutiny in this category are cheaper and fewer than the marketing suggests. Three of the strongest are free, the best paid options sit between thirty and fifty dollars a month, and the most heavily promoted product in the category is promoted mainly by itself. Start with a free scanner, learn what an equivalent market looks like and what fees do to a thin spread, and only pay for coverage once you know which venues you actually want watched. Our guide to how prediction market arbitrage works covers the mechanics, and prediction market data sources compares the underlying feeds these tools are built on.