MarketMaster — Kalshi & Polymarket Edge Scanner + Arbitrage

Free Kalshi & Polymarket arbitrage scanner — cross-platform edge, Kelly sizing, live positions, no backend, no paywall.

NOW IN BETA - MarketMaster is a free, local-first prediction-market edge scanner that turns Kalshi and Polymarket into a single, scored, comparable view. Open the popup on any market page and see the cross-platform price, a concrete YES/NO/HOLD verdict, an edge score, a quarter-Kelly suggested size, and a one-click news context fetch — all running locally in your browser. No backend, no account, no paywall. WHAT IT DOES - Analyzer — Pulls live YES and NO prices from Kalshi and Polymarket for the prediction market you're viewing, normalizes them to cents, flags cross-platform arbitrage when YES on one platform plus NO on the other costs less than 100¢, and recommends a position size using quarter-Kelly off your bankroll. - Scanner — Ranks every active prediction market by a composite edge score combining liquidity, spread, momentum, sweet-spot pricing, and time urgency. Filter by platform or minimum edge. - Trending — Lists markets by 24-hour volume so you can see what's moving right now. Filter by category and platform. - My Markets — A personal watchlist with live prices and price-change sparklines. - Profile + trading journal — When you add an optional Kalshi API key and Polymarket wallet address, MarketMaster shows your live positions on both platforms with COST / VALUE / PNL columns, plus an auto-logged trading journal that records every fill so you can review your edge over time. - Background alerts — A 15-minute background scan checks your subscribed markets and fires an OS notification when a price crosses your threshold. - Auto-fill (opt-in, off by default) — Pre-fills the contract count into the platform's own trade ticket. It never clicks Confirm; you do. WHAT IT DOESN'T DO - Place trades, click Confirm, or move money in any way. - Send any data to a developer server. There are no developer servers. - Collect personal information, run analytics, or use cookies. - Charge anything. Free for everyone. PRIVACY (LOCAL-FIRST, NO BACKEND) MarketMaster is privacy-first by design — there is no developer backend, no telemetry, no analytics, and no account. Everything runs in your browser. Settings, your watchlist, optional API keys, and price history live in chrome.storage.local on your device only. The only network requests MarketMaster makes are direct calls from your browser to: - Kalshi public + authenticated APIs (api.elections.kalshi.com, trading-api.kalshi.com) - Polymarket public APIs (gamma-api.polymarket.com, data-api.polymarket.com, clob.polymarket.com) - PredictionHunt (only if you provide an API key) - Google News RSS (only when you click "Get Market Context") If you provide a Kalshi private key, it stays on your device and is used to sign requests locally with RSA-PSS-SHA256. The key itself is never transmitted. Full privacy policy: https://marketmasterapp.netlify.app/privacy.html NOT FINANCIAL ADVICE Prices, verdicts, edge scores, Kelly suggestions, and arbitrage signals are research tools, not recommendations. The developer is not a licensed financial advisor. Verify market data independently before trading. Prediction-market trading involves real risk including total loss of capital. See terms.html in the extension for the full disclaimer. REQUIREMENTS - Use is limited to jurisdictions where prediction-market trading is legal and you meet the platforms' eligibility requirements. - You must be 18+ (or the age of majority where you live). SUPPORT Found a bug or have feedback? https://buymeacoffee.com/marketmasterapp Learn more at: https://marketmasterapp.netlify.app/