What Is PolyArbitrage?
PolyArbitrage is a Chrome browser extension designed to surface arbitrage opportunities that exist between two prediction market platforms: Polymarket and Kalshi. Rather than requiring a separate desktop application or manual price comparison, it operates inside the Chrome browser environment, making it accessible to anyone who can install an extension from the Chrome Web Store.
Kalshi is a CFTC-regulated US prediction market exchange where users trade event contracts settled in USD. Polymarket is a separate prediction market platform. Because both platforms allow users to take positions on similar or identical real-world events, price discrepancies can occasionally emerge between them — and that is the gap PolyArbitrage is built to identify.
Public details about the extension's inner workings are limited. Based on available information, the core value proposition is straightforward: the extension monitors prices across the two platforms and highlights when a meaningful spread exists that could, in theory, be captured by trading on both sides.
Where It Fits in the Kalshi Ecosystem
Within the broader landscape of third-party Kalshi tools, PolyArbitrage falls into the arbitrage tools category. Kalshi exposes a Trading API — including REST and WebSocket interfaces — that allows third-party developers to build tools that interact with or pull data from the exchange. Cross-market arbitrage tools represent a specific niche: they aim to give traders an informational edge by comparing Kalshi's prices against those on other venues.
PolyArbitrage is a browser extension rather than a standalone trading bot or algorithmic system, which shapes both its strengths and its limitations. It surfaces opportunities for human review rather than executing trades automatically — at least based on the publicly available description.
Who Is It For?
PolyArbitrage is likely most relevant to active prediction market participants who already trade on both Kalshi and Polymarket and want a lightweight, in-browser way to spot pricing discrepancies without building their own monitoring tools. It may appeal to:
- Retail traders looking for an edge across platforms without writing code
- Prediction market enthusiasts who follow similar events on multiple platforms
- Opportunistic arbitrageurs who want to act quickly when spreads appear
It is probably less suited to fully automated or high-frequency arbitrage strategies, given its nature as a browser extension rather than a programmatic trading system.
Typical Use Cases
The primary use case is comparative price monitoring. A user with the extension installed could browse one platform's markets while the extension flags when a corresponding market on the other platform is priced differently enough to warrant attention. The trader would then independently decide whether to act on that signal, taking into account execution, fees, and any platform-specific constraints.
Beyond pure arbitrage, the extension could also serve as a general market-awareness tool — helping traders understand where consensus pricing differs between platforms on the same underlying event.
Things to Weigh When Choosing a Tool in This Category
When evaluating any cross-market arbitrage tool, a few general considerations apply regardless of the specific product:
- Data freshness: How quickly does the tool update prices? Arbitrage windows in prediction markets can be short-lived.
- Coverage: Which markets and event types are compared? Not every Kalshi market will have a Polymarket equivalent.
- Execution responsibility: Browser extensions typically surface opportunities but leave trade execution to the user, introducing manual latency.
- Fee awareness: Transaction costs on both platforms need to be factored in to determine whether a quoted spread is actually profitable.
- Maintenance and reliability: Third-party tools depend on continued compatibility with platform APIs and browser environments; public details about update cadence for PolyArbitrage are limited.
Bottom Line
PolyArbitrage offers a browser-native way to monitor price discrepancies between Polymarket and Kalshi, targeting prediction market traders who operate across both platforms. Its lightweight, extension-based format lowers the barrier to entry compared to building custom monitoring infrastructure. That said, public documentation on its specific capabilities, update frequency, and reliability is limited, so prospective users may want to test it directly via the Chrome Web Store listing before relying on it as part of a trading workflow.