Using the Polymarket Data API: Real-Time Prediction Market Data

Data from prediction markets has emerged as a critical resource for academic researchers, media outlets, and algorithmic trading operations. Through PolyGram, developers gain access to comprehensive APIs that tap into the globe's foremost prediction market information ecosystem.

Available Data Endpoints

Gamma API (Market Data)

GET https://gamma-api.polymarket.com/events
  ?limit=100&active=true&order=volume24hr
  Returns: event metadata, current prices, volume, tags

GET https://gamma-api.polymarket.com/events/{slug}
  Returns: full event with all markets, prices, descriptions

GET https://gamma-api.polymarket.com/markets/{conditionId}
  Returns: single market details, current order book price

CLOB API (Order Book)

GET https://clob.polymarket.com/book
  ?token_id={tokenId}
  Returns: full order book depth (bids/asks)

GET https://clob.polymarket.com/prices/history
  ?market={conditionId}&resolution=1h&startTs=1700000000
  Returns: hourly price history

WebSocket: wss://ws-subscriptions-clob.polymarket.com
  Subscribe to real-time price updates

Python Quickstart

import requests

# Get top prediction markets by volume
r = requests.get(
    "https://gamma-api.polymarket.com/events",
    params={"limit": 10, "active": "true", "order": "volume24hr"}
)
for event in r.json():
    market = event["markets"][0] if event.get("markets") else {}
    prices = market.get("outcomePrices", "[0.5,0.5]")
    import json; p = json.loads(prices)
    print(f"{event['title'][:50]}: YES={float(p[0]):.2%}")

Use Cases

Research dashboards: Monitor how prediction market probabilities shift throughout the lifecycle of particular events
News tools: Identify markets experiencing significant movement in response to emerging developments
Aggregators: Conduct side-by-side analysis of odds on Polymarket, Kalshi, and Metaculus platforms
Alert systems: Trigger notifications whenever a market crosses predetermined volatility boundaries
Academic research: Leverage historical resolution outcomes to evaluate prediction accuracy and forecaster performance

FAQ

Is the Polymarket API free to use?: Yes — market data via the Gamma API carries no cost subject to standard rate restrictions (approximately 100 requests per minute for unauthenticated access). Submitting orders through the CLOB requires an active wallet balance; however, retrieving market information remains complimentary.
Is there a Python library for Polymarket?: Multiple Python libraries maintained by the community are available on GitHub. Look for "polymarket-py" to find the most actively supported implementations.