Using the Polymarket Data API: Real-Time Prediction Market Data for Developers | Kalshi Alternative UK

In this guide

Available Data Endpoints
Python Quickstart
Use Cases
FAQ

Developers and researchers increasingly rely on prediction market data for academic studies, investigative reporting, and algorithmic trading. Through PolyGram, the Polymarket platform—the globe's leading prediction market—offers comprehensive APIs that grant access to an unparalleled dataset for building sophisticated applications.

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 odds shift across time for particular outcomes
News tools: Identify and highlight markets experiencing rapid movement during major announcements
Aggregators: Benchmark pricing across Polymarket, Kalshi, and Metaculus to spot discrepancies
Alert systems: Send notifications whenever a market swings past a specified boundary
Academic research: Leverage historical settlement information to evaluate forecast quality and model performance

FAQ

Is the Polymarket API free to use?: Absolutely—the Gamma API for market data is available at no cost subject to rate restrictions (roughly 100 requests per minute without authentication). Submitting orders via CLOB requires an active wallet, though retrieving data remains complimentary.
Is there a Python library for Polymarket?: Multiple community-developed Python packages are available on GitHub. Look for "polymarket-py" to find the most actively maintained implementations.