Prediction Market Odds API – Polymarket, Kalshi & Manifold in One Schema

Live odds from the three biggest prediction markets – Polymarket, Kalshi and Manifold – normalised into one schema: implied probability (yes price), bid/ask, 24h volume, liquidity, close time and URL. Search by keyword ("fed", "bitcoin", "election") or pull the top markets by volume.

• ✅ Never a silent empty dataset: if a source is down you get a free status: "error" row naming it; if nothing matched you get a free status: "no_results"-type row saying so. Errors and status rows are never charged.
• ✅ Official open-data APIs only – no scraping of websites, no login, no proxies needed
• ✅ One clean, documented schema across all sources
• ✅ Pay only for results: $0.002 per market ($2.00 per 1,000). Errors are free.

Coverage

• Sources: Polymarket (gamma-api.polymarket.com), Kalshi (api.elections.kalshi.com trade API v2), Manifold (api.manifold.markets v0) – public read-only APIs, no key.
• Markets: open markets only; worldwide topics (politics, economics, crypto, tech, science, weather…). Kalshi sports are skipped unless you pass kalshiCategories/keywords.
• Fields: platform, marketId/slug, event, question, outcome label + all outcomes, yes/no price (implied probability), best bid/ask, last price, 24h price change, 24h and total volume, liquidity, open interest, currency, real-money flag, category, status, close/created time, resolution source, URL, fetchedAt. Fields a platform does not publish are null.
• Not covered: order books, trade history, resolved-market archives, Betfair/PredictIt.

When a source is down – error, not empty

• Each platform is fetched independently, with retries on HTTP 429/5xx (honouring Retry-After).
• If a platform still fails, you get one free row {"platform": "Kalshi", "status": "error", "error": "…"} and the other platforms continue. The run still ends SUCCEEDED, so check for status rows.
• If the platforms answered but nothing matched your keywords/volume filter, you get one free row {"status": "no_results", "error": "Polymarket, Kalshi, Manifold answered, but no open market matched …"} – never a silent empty dataset.
• Market rows never have a status of error/no_results, so status in ("error","no_results") separates the two.

Cost example and cost cap

• 3 platforms × 100 markets (default) = up to 300 markets = $0.60 + $0.00005 start. 50 keyword matches ≈ $0.10.
• Cap it two ways: maxItems (total markets, e.g. 100 → max $0.20) and/or Max charge per run (Console → Run options, or maxTotalChargeUsd in the API). When the charge limit is hit the Actor stops cleanly and keeps what it saved. Status rows are free.

What can you use it for?

• Compare the same event across venues and spot price gaps (arbitrage / research)
• Feed dashboards, newsletters and trading bots with probabilities on macro, crypto, politics and tech
• Track market sentiment over time with Apify schedules (every 5 min, hourly, daily)
• Academic / journalism research on forecasting accuracy

Input

Field	What it does
keywords	e.g. fed, bitcoin, trump – empty = top markets by 24h volume
platforms	polymarket, kalshi, manifold (default all)
maxMarketsPerPlatform	Billable results cap per venue
maxItems	Optional total billable cap for the whole run (empty = no total cap)
minVolume24h	Skip illiquid markets
kalshiCategories	e.g. Economics, Crypto, Politics (default: all non-sports)
kalshiMaxEvents	How many Kalshi events to expand

Example input:

{
  "keywords": [
    "fed",
    "bitcoin"
  ],
  "platforms": [
    "polymarket",
    "kalshi",
    "manifold"
  ],
  "maxMarketsPerPlatform": 25
}

Output

Each result is one row in the dataset (download as JSON, CSV, Excel or via API). Example:

{
  "platform": "Polymarket",
  "marketId": "2589813",
  "marketSlug": "will-the-fed-increase-interest-rates-by-25-bps-after-the-october-2026-meeting-20260617190324032",
  "eventId": "606422",
  "eventTitle": "Fed Decision in October?",
  "question": "Will the Fed increase interest rates by 25 bps after the October 2026 meeting?",
  "outcomeLabel": "25 bps increase",
  "outcomes": [
    {
      "name": "Yes",
      "price": 0.045
    },
    {
      "name": "No",
      "price": 0.955
    }
  ],
  "yesPrice": 0.045,
  "noPrice": 0.955,
  "bestBid": 0.04,
  "bestAsk": 0.05,
  "lastPrice": 0.04,
  "priceChange24h": -0.03,
  "volume24h": 784045.448559,
  "volumeTotal": 14393749.342364,
  "liquidity": 1546726.8007,
  "openInterest": null,
  "currency": "USDC",
  "isRealMoney": true,
  "category": null,
  "status": "open",
  "closeTime": "2026-10-29T03:59:00Z",
  "createdTime": "2026-06-17T23:05:57.870064Z",
  "resolutionSource": "https://www.federalreserve.gov/monetarypolicy/fomccalendars.htm",
  "url": "https://polymarket.com/event/fed-decision-in-october-20260617190323537",
  "fetchedAt": "2026-10-24T16:41:52+00:00"
}

Resolution rules next to the odds

Markets with the same question can resolve differently on each platform. Every row includes rulesText (Polymarket description, Kalshi primary + secondary rules, Manifold description; whitespace collapsed, max 2,000 characters) and, for Kalshi, canCloseEarly. Read the rules before treating two markets as the same bet. No platform login is needed; only public endpoints are used.

Pricing

Pay-per-event, no subscription:

Event	Price
Market snapshot (market)	$0.002 ($2.00 / 1,000)
Actor start	$0.00005

Error rows and empty results are never charged. Set Max charge per run in Apify Console to cap your spend – the Actor stops cleanly when the limit is reached.

Option names (shared across our open-data Actors)

The five Actors in this pack (Prediction Markets, US Building Permits, EU Company Registry, UK Public Tenders, EU Fuel Prices) use the same names for the same job:

Job	Option	Notes
Free-text filter	keywords (array)	EU Company Registry uses query (one company name) + registrationNumbers
Date window	daysBack + …From / …To	issuedFrom/To (permits), publishedFrom/To (tenders)
Total billable cap	maxItems	available in all five; per-source caps (maxMarketsPerPlatform, maxItemsPerCity, maxResultsPerCountry, maxPagesPerSource) still work
Only new rows on schedules	onlyNewSinceLastRun	EU Fuel Prices: onlyChangedSinceLastRun (prices that changed)
Which sources	platforms / cities / countries / sources	the natural unit of each source

Status rows always use the same status values: error / source_unavailable (source down), no_results / no_match / not_found (source answered, nothing matched), no_new (nothing new since last run). They are never charged.

FAQ

Is the data official?
Yes – it comes from each venue's public, read-only market-data API (no login, no wallet, no trading). The Actor never places orders.

Are prices probabilities?
yesPrice is the last/mid price of the YES contract on a 0–1 scale, which is the market-implied probability. Manifold uses play money (isRealMoney: false).

Why is Kalshi slower?
Kalshi lists ~16,000 open events; the Actor filters them first and then fetches markets per event (5 in parallel) to avoid the tens of thousands of combo markets.

Do you collect user data?
No. Creator / trader names are dropped; only market-level data is returned.

Can I get historical prices?
Not yet – schedule the Actor to build your own time series. A price-history mode is on the roadmap.

Legal & data sources

This Actor only reads public data published by government bodies or by the platforms' own public APIs under open licences (each row has source/license or url fields where available). It returns organisation-level data and deliberately excludes personal data. You are responsible for using the data in line with the source licence and applicable law (e.g. GDPR).

Integrations

Schedule runs, then push results to Google Sheets, Slack, webhooks, Zapier, Make or your database with Apify integrations, or call the Actor from the Apify API / Python / JavaScript clients.