PredictMirror

PredictMirror is a Polymarket paper trading simulator that lets you practice on every market without putting a single dollar at risk. The extension overlays a trading panel directly on any Polymarket and Kalshi event page, pulling live prices from the real order book so your simulated trades reflect exactly what you would have paid or received on the actual market. Start with $1,000 in virtual capital, your own Polymarket paper account with no wallet or signup required. Place BUY and SELL trades on any outcome across sports, crypto, politics, culture, and esports markets. PredictMirror calculates fees and slippage using Polymarket's exact formula, so the numbers match what you would see on the real platform down to the cent. WHAT MAKES IT ACCURATE Most paper trading tools use simplified math that drifts from real platform numbers. PredictMirror is built on a Polymarket paper trading engine that walks the actual order book depth to account for slippage on thin markets, applies the correct fee rate per market category, and mirrors the same share-based input format Polymarket uses for sell orders. The result is a simulation you can actually trust when you decide to trade for real. KEY FEATURES - Live prices from Polymarket's real order book, updated as you trade - Accurate fee calculation per market category, matching Polymarket's published schedule - Full order book depth walking so slippage on illiquid markets is simulated correctly - BUY and SELL simulation with percentage chips for quick position sizing on sells - Portfolio view showing all open positions with live unrealized P&L - Trade history with closed position records and realized gains and losses - Stats dashboard with win rate, current streak, and a 30-day activity heatmap - Shareable trade cards you can copy or download to show your calls - Works across all Polymarket categories including sports and esports sub-markets - All data stored locally in your browser, no account required, no data leaves your device WHO IT IS FOR A lot of people ask whether you can paper trade on Polymarket before putting real money in. The answer is yes, with PredictMirror. It is built for prediction market newcomers who want to build intuition in a paper trading sandbox before committing real capital, experienced traders who want to test a thesis on a specific market without exposure, and anyone who follows events on Polymarket and wants to keep an honest record of how their reads perform over time. HOW TO GET STARTED 1. Install PredictMirror and open any event page on the supported platforms 2. The trading panel slides in alongside the page automatically 3. Pick a side, enter an amount, and place your first simulated trade 4. Track your open positions and review your performance at any time No wallet connection required. No account to create. PredictMirror runs entirely inside your browser using Polymarket's public data. Uninstalling the extension removes all locally stored data.