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

In this guide

Available Data Endpoints
Python Quickstart
Use Cases
FAQ

Quantitative analysts, researchers, and media organisations have increasingly relied on prediction market intelligence for decision-making. PolyGram provides developers with comprehensive API access to the globe's foremost prediction market, enabling sophisticated integrations across the entire dataset 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 probability shifts across specific prediction markets in real time
News tools: Identify markets responding to emerging developments and news cycles
Aggregators: Benchmark odds between Polymarket, Kalshi, and Metaculus platforms
Alert systems: Trigger notifications when market movement exceeds configured parameters
Academic research: Analyse historical settlement records to evaluate forecast quality and model performance

FAQ

Is the Polymarket API free to use?: Yes — market data via the Gamma API carries no cost, though rate limits apply (~100 requests per minute without authentication). Submitting orders on the CLOB requires wallet funding, though querying order book data remains complimentary.
Is there a Python library for Polymarket?: Multiple community-built Python packages are available on GitHub. Look for "polymarket-py" to find actively maintained implementations.