Prediction Markets Odds API: Kalshi + Polymarket in one schema

Get live odds, bid/ask, spread, 24h price change, volume, open interest and resolution rules from Kalshi and Polymarket as one clean, normalized table. Every row is a single tradable outcome, priced in 0–1 probability terms, so you can compare venues side by side, feed a model, or build a dashboard.

• Official public APIs only. No login, no API keys, no proxies, no browser. That makes runs fast (≈4 s for 40 rows) and cheap.
• One schema for both venues. The same field names are used whether the row came from Kalshi or Polymarket.
• Filters: keywords, categories (Kalshi categories / Polymarket tags), minimum 24h volume, venue.
• Skips noise: Kalshi's thousands of auto-generated multi-leg parlay markets (KXMVE…) are excluded by default.
• Ranked by activity: the most-traded markets come first.

Use cases

• Cross-venue arbitrage and price-gap scans (e.g. the same Fed decision priced on both venues)
• Feeding forecasts or trading bots with consistent odds snapshots (schedule it every 5–15 minutes)
• Newsletters, dashboards and research on election, macro, sports and crypto odds

Input

Field	Description
venues	kalshi, polymarket or both (default both)
searchTerms	Keep markets whose question/outcome/event contains any of these words
categories	e.g. economics, politics, sports, crypto
minVolume24h	Skip thin markets (contracts on Kalshi, USD on Polymarket)
maxResults	Total rows; split evenly across venues
excludeParlays	Skip Kalshi multi-leg combos (default true)
maxPagesPerVenue	Safety cap on pages scanned

Example:

{"venues": ["kalshi", "polymarket"], "searchTerms": ["fed", "rate", "inflation", "cpi"], "minVolume24h": 100, "maxResults": 40}

Output (real rows from a test run on Oct 31, 2026)

{
  "venue": "kalshi",
  "market_id": "KXFEDDECISION-26DEC-C26",
  "event_id": "KXFEDDECISION-26DEC",
  "event_title": "Fed decision in Dec 2026?",
  "question": "Will the Federal Reserve Cut rates by >25bps at their December 2026 meeting?",
  "outcome": "Cut >25bps",
  "category": "Economics",
  "tags": [
    "Economics"
  ],
  "yes_price": 0.005,
  "yes_bid": 0.0,
  "yes_ask": 0.01,
  "spread": 0.01,
  "last_price": 0.01,
  "price_change_24h": 0.0,
  "volume_24h": 654.0,
  "volume_total": 166753.61,
  "volume_unit": "contracts",
  "open_interest": 158415.31,
  "liquidity": null,
  "close_time": "2026-12-09T18:59:00Z",
  "rules": "If the Federal Reserve does a Cut of   25bps on December 09, 2026, then the market resolves to Yes.",
  "url": "https://kalshi.com/markets/kxfeddecision",
  "scraped_at": "2026-11-01T05:58:27.092435+00:00"
}

{
  "venue": "polymarket",
  "market_id": "0xb9aee520bf51ac5f00b5c43e54ef9245bc9fcdef866ce8a33025f9a441cc651d",
  "event_id": "fed-decision-in-december-20260729232808632",
  "event_title": "Fed Decision in December?",
  "question": "Will the Fed decrease interest rates by 50+ bps after the December 2026 meeting?",
  "outcome": "50+ bps decrease",
  "category": "Fed",
  "tags": [
    "Fed",
    "fomc",
    "Trump",
    "Economy",
    "Fed Rates",
    "Kevin Warsh",
    "Global Rates",
    "Economic Policy",
    "Macro Indicators",
    "Recurring"
  ],
  "yes_price": 0.0035,
  "yes_bid": 0.003,
  "yes_ask": 0.004,
  "spread": 0.001,
  "last_price": 0.004,
  "price_change_24h": -0.0005,
  "volume_24h": 12702.31,
  "volume_total": 1849150.813975,
  "volume_unit": "usd",
  "open_interest": null,
  "liquidity": 180398.82363,
  "close_time": "2026-12-09T23:59:00Z",
  "rules": "The FED interest rates are defined in this market by the upper bound of the target federal funds range. The decisions on the target federal funds range are made by the Federal Open Market Committee (FOMC) meetings.\n\nThis…",
  "url": "https://polymarket.com/event/fed-decision-in-december-20260729232808632",
  "scraped_at": "2026-11-01T05:58:27.092435+00:00"
}

Fields: venue, market_id, event_id, event_title, question, outcome, category, tags, yes_price (bid/ask mid), yes_bid, yes_ask, spread, last_price, price_change_24h, volume_24h, volume_total, volume_unit, open_interest, liquidity, close_time, rules, url, scraped_at. A RUN_SUMMARY record in the key-value store gives per-venue counts.

Pricing (suggested)

Pay per event: market-row at $0.002 ($2.00 per 1,000 rows), with store tiers Bronze $1.80 / Silver $1.60 / Gold $1.40 per 1,000. Benchmarks in Apify Store on Oct 31, 2026: single-venue Kalshi actors charge about $1.50/1K rows (lergassy), $1.50/1K (scrapebench), and $4/1K rows plus $10/1K trades (scrapemint). We charge a small premium because this actor covers both venues in one normalized schema. Platform compute is negligible because the actor makes only HTTP JSON calls.

Notes

Data comes from Kalshi's public market data API and Polymarket's public Gamma API. This is not financial advice. Prices are snapshots at scraped_at.