Paper Trading
Practice book at real venue prices. No money at risk.
The tool runs at /paper and needs a $49.99/mo membership. There is no free tier and no trial, so opening it signed out lands on the pricing page rather than the board. This page is the open documentation of what it does.
Paper Trading is a practice book: ten thousand dollars of fake money, spent at prices taken from the live venues. You search a market, choose a side, stake an amount, and the book buys whole contracts at that side's quoted price. Later you close the position at the current mark and the trade moves into a history log.
The point is the loop, not the score. Opening a position and then watching a mark move against you for three days is a different education from reading about it, and it costs nothing.
How an order is filled
Prices are quoted per contract in cents, and a contract pays one dollar if its side is right and nothing if it is not. The book only accepts a price between one and ninety-nine cents — outside that there is no real two-sided market to practise against. Your stake buys whole contracts, so the actual cost is contracts multiplied by price and can come in under the stake you typed; the remainder stays as cash.
All the money arithmetic runs in integer cents, so repeated buying and closing cannot accumulate rounding drift and the balance always reconciles.
Marks, closing, and the record
Open positions carry a last-known mark. A sweep re-reads each position's market and updates it; if a market cannot be re-found on a sweep the position keeps its last known mark and the row says so, rather than silently showing a stale number as fresh.
Closing sells at the current mark: proceeds return to cash and the closed trade is written to history with entry, exit, contracts, cost, proceeds and profit. The header carries practice cash, open value at last mark, and total balance against the ten thousand you started with.
Where the market list comes from
The picker searches both venues. Kalshi rows arrive from the catalog with their prices attached. Polymarket search returns events rather than individual markets, so the page expands the chosen event through Polymarket's public API to list its markets with live prices, and re-reads a single market the same way on a mark sweep.
That means the practice book trades the same instruments as the real venues, with the same outcome names, at prices that were real when you clicked.
Starting over
A reset returns the book to a clean ten thousand and wipes both positions and history. It is there because a practice account whose only permanent record is one catastrophic week stops being useful practice.
Everything — cash, positions, history — lives in your browser's local storage under keys that have not changed since the feature shipped, so an existing practice book is not silently wiped by an update.
What it cannot tell you
Every tool has a boundary, and knowing where it sits is the difference between using one well and being misled by it. For Paper Trading:
- No fees and no slippage are modelled. A real fill costs more than a paper one, and on Kalshi the per-contract fee alone is meaningful on tight trades.
- There is no order book. You always fill your whole size at the quoted price, which is exactly what a thin market will not let you do.
- Positions do not settle themselves when a market resolves. You close them at the current mark; the book has no settlement engine.
- A practice record is not a track record. Nothing is stored server-side and nothing here is published or verified.
- It lives in one browser. Clearing site data deletes the book, and it does not follow you to another device.
- Prices are read at the moment you open, mark or close. Between those moments the venue's book has moved and the practice book has not.
What it is built on
- Polymarket gamma: event and market lookups by slug, for live prices on the chosen side.
- Kalshi trade-api v2 market data, through the same catalog the Market Browser searches.
- Your browser's local storage, which holds cash, open positions and closed-trade history.
Related reading
- Markets Browser: Search Polymarket, Kalshi, and Manifold in One Place — Guide
- One-Click Copy: How to Execute Sharp-Money Trades on Polymarket and Kalshi — Guide
- Kelly Criterion for Prediction Markets: A Fee-Aware Position Sizing Calculator for Polymarket and Kalshi — Guide
- Bankroll Management for Prediction Market Trading: Position Sizing, Kelly Staking, and Drawdown Control — Strategy
Tools that pair with it
Search every market on Polymarket, Kalshi, and Manifold.
Fee-aware position sizing, hedges, and a drawdown simulation.
Paste a Polymarket wallet and read its book, live.
WhaleTracks is informational analytics, not financial advice. Market data comes from Polymarket, Kalshi and Manifold's public APIs; WhaleTracks is not affiliated with any of them. Past performance does not guarantee future results.