Polymarket & Kalshi Prediction Market Scraper

What does Polymarket & Kalshi Prediction Market Scraper do?

This Actor extracts live prediction market data from Polymarket and Kalshi — the two largest prediction markets — and delivers it as one clean, normalized dataset. Every row is one market with its current odds, implied probability, bid/ask, volume, liquidity, category, close date, and resolution rules. Both platforms come back in the same shape, so comparing odds across them needs no cleanup at all.

It talks directly to the platforms' public JSON APIs — no browser, no screenshots, no flaky selectors — which makes runs fast, cheap, and stable.

Why use this Actor?

• Two platforms, one schema — Polymarket and Kalshi rows share the exact same field set. Filter platform and compare the same question's odds side by side.
• The data points that matter — implied probability, yes/no prices, best bid/ask, spread, last trade, 24h and total volume, open interest, settlement results, and full resolution rules.
• Search and filter server-smart — keyword search uses Polymarket's own relevance ranking; Kalshi is scanned and matched word by word. Filter by category, volume, liquidity, or close-date window.
• Resolved markets included — pull settled markets with final prices and the winning outcome, ready for backtesting and model calibration.
• Built for pipelines — every row always has every field (null when a platform doesn't provide it), ISO 8601 dates, numeric types, absolute URLs.

How much does it cost?

You pay per market returned. A run with maxMarkets: 200 returns up to 200 markets and typically finishes in well under a minute. A daily snapshot of the top 500 markets of both platforms costs a few cents per day. Use maxMarkets to put a hard ceiling on any run — unlimited runs without narrowing filters are automatically capped at 10,000 markets.

Input

Field	Type	Description	Example
platforms	array	Which platforms to scrape (polymarket, kalshi). Both by default; the result cap is split evenly.	["polymarket", "kalshi"]
searchQuery	string	Keyword search. Polymarket is searched server-side by relevance; Kalshi is matched on question, event title, and outcome.	"bitcoin"
category	string	Category/tag filter, case-insensitive substring (politics, sports, crypto, economics, weather, …).	"weather"
status	string	active (trading now, default), resolved (settled, with final prices and winners), or all.	"active"
minVolume	integer	Skip markets with total volume below this (USD on Polymarket, contracts on Kalshi).	1000
minLiquidity	integer	Skip markets with liquidity below this (USD). Polymarket only — Kalshi does not publish liquidity.	500
endingAfter / endingBefore	date	Only markets closing inside this window — e.g. everything that resolves this week.	"2026-09-01"
maxMarkets	integer	Hard cap on returned markets (= billed results).	200

An empty input works: it returns the top active markets of both platforms, ordered by 24-hour volume on Polymarket.

Output

One row per market:

{
    "platform": "kalshi",
    "marketId": "KXBTCD-26AUG28-T85000",
    "question": "Will Bitcoin be above $85,000 by Aug 28, 2026 at 11:59 PM ET?",
    "eventId": "KXBTCD-26AUG28",
    "eventTitle": "Bitcoin above $85,000?",
    "seriesTicker": "KXBTCD",
    "outcomeLabel": null,
    "outcomes": ["Yes", "No"],
    "outcomePrices": [0.02, 0.98],
    "yesPrice": 0.02,
    "noPrice": 0.98,
    "yesBid": 0.01,
    "yesAsk": 0.02,
    "spread": 0.01,
    "lastTradePrice": 0.02,
    "priceChange24h": null,
    "probability": 2,
    "volume": 168340.25,
    "volume24h": 4120.5,
    "liquidity": null,
    "openInterest": 52310.75,
    "category": "Financials",
    "tags": ["Financials"],
    "status": "active",
    "result": null,
    "createdAt": "2026-08-21T14:00:00Z",
    "endDate": "2026-08-29T03:59:00Z",
    "url": "https://kalshi.com/markets/kxbtcd",
    "image": null,
    "rules": "If the price of Bitcoin is above $85,000 at the expiration time, then the market resolves to Yes.",
    "scrapedAt": "2026-08-27T14:30:00.000Z",
    "runId": "AbC123..."
}

Field notes:

• Prices are USD per share (0–1); a share pays $1 if the market resolves in its favor. probability is the yes/first-outcome price × 100.
• volume is platform-native: USD on Polymarket, contracts on Kalshi (each contract pays $1 max, so the scales are comparable).
• result — Kalshi's official settlement, or the winning outcome of a resolved Polymarket market derived from its settled prices.
• Sports markets on Polymarket trade team-vs-team (e.g. outcomes: ["Vitality", "9z"]) — yesPrice/noPrice are null there and outcomePrices carries both sides.
• Fields a platform doesn't provide are null, never omitted: openInterest and seriesTicker are Kalshi-only; liquidity, priceChange24h, and image are Polymarket-only.

Tips and tricks

• Track odds over time: schedule the Actor (e.g. hourly) with the same input and diff snapshots by marketId — runId and scrapedAt on every row keep runs apart after export.
• Cross-platform comparison: search the same topic (e.g. "fed rate") with both platforms enabled and join on the question text — price differences between Polymarket and Kalshi are visible immediately.
• "What resolves this week": set endingBefore seven days out with status: "active".
• Skip dead markets: minVolume: 1000 removes markets nobody trades.
• Kalshi ordering: Kalshi has no server-side sort, so its rows arrive in exchange order — use minVolume or a category to focus its half of the results. Polymarket rows arrive ordered by 24-hour volume.
• Backtesting: status: "resolved" returns settled markets with final prices and winners.

Integrations

The dataset works with every Apify integration: export to JSON, CSV, Excel, push to Google Sheets, trigger webhooks on finish, or query via the Apify API from Python/Node. Typical setups: a scheduled run feeding a Google Sheet dashboard of weekly odds, or the Apify API pulling fresh markets into a trading-signal pipeline.