Prediction Market Data: Where to Get It, What It Costs and How to Use It

TL;DR

• Prediction market data covers prices (implied probabilities), volume, open interest, order books, trades and settled outcomes, and on-chain platforms also expose wallet-level activity.
• Polymarket and Kalshi both publish market data through documented APIs, and their docs show public reads without an account key. Neither set of docs publishes pricing or rate limits in the pages I checked.
• The Polymarket leaderboard ranks traders by profit and loss or by volume across Today, Weekly, Monthly and All periods and by category, and it does not explain how those rankings are calculated.
• PredictionHero lines up prediction market data from Polymarket, Kalshi, Limitless, Predict.Fun and Opinion on one screen, so a price on one platform can be checked against the others.

Trying to find prediction market data and ending up with five tabs and a Polymarket leaderboard screenshot? Most of what you need is public. The platforms publish their own prices and documented APIs, analytics sites rank traders and chart volume, and an aggregator puts every platform side by side.

The harder part is knowing what each source actually tells you. This guide covers where to find it, what it costs, how to read the Polymarket leaderboard, and how to use any of it without being misled.

What Is Prediction Market Data?

Prediction market data is the record of what traders did and what the market implies. The most common pieces are:

• Price. The market's implied probability, from $0 to $1 per Yes contract.
• Volume. The running total of trades, which says how much activity a market has seen. Our guide to what volume means explains why it is not the same as money at stake.
• Open interest. The value currently held in outstanding positions.
• Order book. The bids and asks that sit behind the price, which show how deep a market is.
• Trades and settlements. Individual fills, and how each market finally resolved.

Platforms that run on a blockchain add a sixth layer, because every fill is recorded against a wallet address. That is where leaderboards and whale tracking come from. If any of those terms are new, our prediction market glossary defines them.

Where Can You Get Prediction Market Data?

There are four kinds of source, and each answers a different question.

No single source covers everything. A platform shows its own market and nothing else. An analytics tool shows trader behavior but not the other platforms' prices. An aggregator is built to compare, not to rank traders.

What Data Does Polymarket Offer?

Polymarket documents its market data in sections: discovering markets, market details, prices and order books (including how prices have changed over time), analytics and real-time data. It also publishes Chainlink time-weighted prices for crypto markets.

The analytics reads are the most useful for research. Polymarket's documentation lists endpoints for the trader leaderboard, the biggest winning positions, open interest in USDC, the largest holders of each outcome, live volume by event, and recent trades with side, price, size, outcome, wallet and timestamp.

The docs' examples make these calls without credentials, and they do not publish rate limits or pricing on the pages I checked. Treat that as a reason to check the current documentation before building anything that depends on volume.

What Is the Polymarket Leaderboard and How Do You Read It?

The Polymarket leaderboard is a public ranking of traders. The page shows tabs for Today, Weekly, Monthly and All, a category filter, and two sort options: Profit/Loss and Volume. A separate section lists the biggest wins for the selected period.

The same data is available through Polymarket's API. You choose a period (day, week, month or all), a category such as politics, sports, crypto, economics or weather, and whether to rank by profit and loss or by volume. Each entry returns a rank, the trader's wallet address, a username, volume and profit and loss. The documented limit is 50 rows per request, with an offset for paging.

Read it with three cautions in mind.

First, the page does not say how rankings are calculated. It does not state whether profit is realized or includes open positions, and the API spec does not state units for volume or profit. Check before you quote a figure.

Second, a ranking shows results, not skill. A trader can top a weekly board on one large position. Our guide to spotting a prediction market whale covers how to read a big wallet, and our piece on fake volume covers why volume rankings can mislead.

Third, access differs by region. The leaderboard page notes that trading is blocked in the United States on polymarket.com and points to polymarket.us. Our guide to Polymarket in the US explains the split.

What Data Does Kalshi Offer?

Kalshi publishes four market-data endpoints that need no authentication headers, at external-api.kalshi.com/trade-api/v2. They return series, markets, events and the order book for a market.

A market returns its ticker, title, the Yes bid price in dollars and its volume. The order book returns bid levels for Yes and No, not asks. Live streaming over WebSocket does require authentication.

Kalshi also splits its data into live and historical tiers, with a cutoff endpoint that says what has moved to the archive. The pages I checked state no pricing and no rate limits. Our Kalshi API guide covers access, endpoints and limits in more detail.

What About Limitless, Predict.Fun and Opinion?

Each of the other three platforms publishes its own documentation and market board, and coverage varies, so check each one directly. They are worth including because they price the same questions differently.

Limitless runs on Base. Predict.Fun and Opinion run on BNB Chain. Because their trades settle on a blockchain, they leave on-chain records that analysts can query, which is how community dashboards track volume and wallets.

What Does Prediction Market Data Cost?

Much of it is free to view. The documented public reads on Polymarket and Kalshi need no account key, and neither set of docs I checked lists a price.

Analytics tools mix free and paid tiers. Polymarket Analytics offers a free tier with market analytics and trader leaderboards, and it sells paid plans for heavier use. Dune hosts public community dashboards, and heavier or enterprise access is sold separately, so check its plan limits before you depend on it.

Community dashboards come with a catch. They are built by individual analysts, so figures can move as the query changes. Use them for direction, and name the dashboard and its author when you cite one.

How Do You Use Prediction Market Data Without Being Misled?

Start with the same four habits for any source.

1. Timestamp it. A price is a snapshot. Write down when you pulled it, and say what platform it came from.
2. Compare platforms. Right now a headline market on Polymarket is priced one way, and the same market on Kalshi is priced differently. A gap is normal, and our piece on why odds disagree explains what causes it.
3. Look past the price. Check volume, open interest and the spread. A thin market is closer to a few opinions than a consensus.
4. Cite it carefully. A market price is a probability at one moment, not a measured result. Our guide on how to cite prediction market data shows how to word it.

If you are building a dataset, be careful with history. Resolved markets are not a random sample, and our guide to backtesting covers the traps. If you want to watch a market over time instead, see how to track prices across platforms.

How Does PredictionHero Fit In?

PredictionHero is a read-only aggregator. It lines up prediction market data from Polymarket, Kalshi, Limitless, Predict.Fun and Opinion, so you can see the same event on every platform without opening five tabs. It does not hold funds or place trades.

It also shows a cross-platform consensus probability and where each platform sits relative to it. That is useful when a question is too important to trust to one crowd. Journalists can follow a ready-made routine in our journalism workflow.

Sources

• Polymarket Documentation. "Market Data Overview." docs.polymarket.com
• Polymarket Documentation. "Analytics." docs.polymarket.com
• Polymarket Documentation. "Get trader leaderboard rankings." docs.polymarket.com
• Polymarket. "Leaderboard." polymarket.com
• Kalshi API Documentation. "Quick Start: Market Data." docs.kalshi.com
• Kalshi API Documentation. "Historical Data." docs.kalshi.com
• Dune. "Prediction markets overview." dune.com

PredictionHero aggregates publicly available prediction market data for informational purposes only. This is not financial advice. Prediction markets may not be available in all jurisdictions.