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

Developers, researchers, and analysts increasingly rely on prediction market information for building tools, conducting studies, and informing decisions. The Polymarket platform, available through PolyGram, provides comprehensive APIs that grant access to one of the world's most extensive prediction market datasets.

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 specific events
News tools: Identify markets experiencing significant movement in response to emerging stories
Aggregators: Examine probability differences between Polymarket, Kalshi, and Metaculus platforms
Alert systems: Send notifications whenever a market crosses predetermined price boundaries
Academic research: Leverage resolved market outcomes to evaluate prediction accuracy and forecasting performance

FAQ

Is the Polymarket API free to use?: Yes — market data through the Gamma API is available at no cost, subject to standard rate limits (approximately 100 requests per minute for unauthenticated access). Submitting orders on the CLOB requires wallet funding, though retrieving data remains free of charge.
Is there a Python library for Polymarket?: Community developers have created and maintain several Python libraries available on GitHub. Look for "polymarket-py" to discover the most actively supported implementations.