Best Prediction Market Arbitrage Bots 2026: Cross-Platform Arb Ranked

Cross-platform arbitrage is the most mathematically rigorous strategy in prediction markets. When the same event is priced differently on Polymarket vs. Kalshi — or on prediction markets vs. sportsbooks — you can lock in a profit regardless of the outcome when both legs fill at the quoted prices. The challenge is execution: finding spreads fast, executing both legs reliably, and accounting for fees on every platform.

This guide covers the real arbitrage tooling available in 2026 — and it is honest about what that toolkit actually is. There is no independently verifiable, turnkey paid “arb bot” you can subscribe to and trust to execute both legs for you. Earlier versions of this page ranked products like PolyArb Pro, CrossMarket Agent, ArbScanner, and SpreadHunter with prices and speed claims; we could not confirm any of them exist, so we removed them. What remains is real: a free calculator, open-source scanners, and the SDK you use to build your own executor.

For platform-specific arb tooling, see Best Arbitrage Bot for Polymarket and Best Arbitrage Bot for Kalshi.

Three Types of Prediction Market Arbitrage

1. Cross-Platform Arb (Polymarket ↔ Kalshi)

The same event priced differently across platforms. Most consistent edge in 2026.

Example: “Will the Fed cut rates in March?”

• Kalshi YES price: 62¢ → Kalshi NO price: 38¢
• Polymarket YES price: $0.57 → Polymarket NO price: $0.43

Buy YES on Polymarket ($0.57) + Buy NO on Kalshi (38¢ = $0.38) = $0.95 total cost. One of them pays $1.00. Guaranteed $0.05 profit (5.3% return) before fees.

2. Prediction Market ↔ Sportsbook Arb

When prediction market odds diverge from sportsbook lines on the same event (common in sports markets). As more CFTC-regulated venues launch sports contracts, the arb surface area is expanding. OG.com (Crypto.com’s prediction market) offers sports-focused contracts with parlays, but currently has no API — making it a potential future arb venue to monitor once programmatic access becomes available.

3. Intra-Platform Arb

Within a single platform — correlated markets diverging, or YES+NO mispricing. Thinnest spreads, highest competition.

The Real Arbitrage Tools (2026)

No star ratings, no invented “fastest scanner” — these are the tools that genuinely exist. The detection layer is real and mostly free; the execution layer is something you assemble yourself.

How Cross-Platform Arb Works

Price Normalization

The first challenge is comparing prices across platforms with different formats:

def normalize_price(polymarket_price=None, kalshi_price=None):
    """Convert to common 0-1 probability format."""
    if polymarket_price is not None:
        return polymarket_price       # Already 0.00-1.00
    if kalshi_price is not None:
        return kalshi_price / 100     # Convert cents to 0.00-1.00

Edge Calculation After Fees

A raw spread means nothing without accounting for fees:

def calculate_arb_edge(yes_price_a, no_price_b, fee_a=0.02, fee_b=0.02):
    """Calculate arbitrage edge after platform fees."""
    cost_yes = yes_price_a * (1 + fee_a)
    cost_no = no_price_b * (1 + fee_b)
    total_cost = cost_yes + cost_no
    payout = 1.00  # Winner pays $1.00
    edge = payout - total_cost
    roi = edge / total_cost * 100
    return {"edge": edge, "roi_pct": roi, "total_cost": total_cost}

For live arb detection, use the Cross-Market Arb Finder or the Arbitrage Calculator.

The Real Tools in Detail

EventArb — the free calculator

EventArb is a free cross-platform arbitrage calculator and alert service for Polymarket and Kalshi. It is the most useful detection tool for most people because it does the price-normalization and fee-adjusted edge math for you and surfaces live opportunities. Be precise about what it is: a calculator and alerting layer, not an executor. It tells you when a spread exists; placing and managing both legs is on you. For a trader who wants to act manually on confirmed spreads, this is the practical starting point — and it costs nothing.

akhan280/event-contract-arbitrage — open-source cross-platform scanner

This open-source scanner (github.com/akhan280/event-contract-arbitrage) watches for the same event priced differently across Polymarket and Kalshi. Because the code is open, you can read exactly how it normalizes prices and where it draws the edge threshold, then adapt it. It is a scanner, not a hosted product — you run it yourself. For anyone serious about cross-platform arb who wants transparency over a black box, this is the reference implementation to study.

ImMike/polymarket-arbitrage — open-source intra-Polymarket scanner

For the third arb type — intra-platform mispricing (YES+NO and correlated-market divergence within Polymarket) — ImMike/polymarket-arbitrage is an open-source scanner you self-host. Intra-market spreads are the thinnest and most competitive, so treat this as a learning tool and a base to extend rather than a money printer.

pmxt — build your own executor

Detection is the easy half; reliable two-legged execution is the hard half, and no free tool hands it to you. pmxt is an open-source, MIT-licensed SDK that gives you a unified, CCXT-style API across Polymarket, Kalshi, and Limitless. Pair a scanner (above) with pmxt and you have the two pieces of a real arb system: something that finds the spread and something that places both orders. This is the honest answer to “where is the turnkey arb bot” — you assemble it, and pmxt is the execution layer.

OctoBot (arb module)

OctoBot is a genuine open-source trading bot (GPL-3.0) with paid cloud tiers. Its prediction-market arbitrage capability is real but explicitly “under development,” and its Kalshi support is limited compared to Polymarket. It is worth watching and experimenting with at zero upfront cost, but do not rely on it as a finished cross-platform arb executor today.

Capital Requirements

See Also

• Best Arbitrage Bot for Polymarket — Polymarket-specific arb rankings
• Best Arbitrage Bot for Kalshi — Kalshi-specific arb rankings
• Cross-Market Arbitrage Guide — Strategy deep-dive
• Cross-Market Arb Finder Tool — Live arb scanner
• Arbitrage Calculator — Calculate edge and stake splits
• Prediction Market API Reference — API documentation for both platforms
• Agent Betting Glossary — Key terms defined
• Agent Marketplace — Browse and compare all agents

Rankings updated March 2026. Not financial advice. Built for builders.