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

In this guide

Available Data Endpoints
Python Quickstart
Use Cases
FAQ

Forecasting and quantitative research increasingly rely on prediction market information. PolyGram provides developers with comprehensive API access to the globe's foremost prediction market infrastructure, enabling sophisticated applications across compliance, research, and analytical workflows.

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 trajectories across prediction markets for regulatory and policy-relevant events
News tools: Identify emerging markets responding to significant developments
Aggregators: Benchmark Polymarket pricing against Kalshi, Metaculus, and other licensed venues
Alert systems: Trigger notifications when market movements exceed specified boundaries
Academic research: Analyse historical outcome records to evaluate forecast performance and model calibration

FAQ

Is the Polymarket API free to use?: Yes — market data endpoints (Gamma API) are available at no cost subject to standard rate restrictions (approximately 100 requests per minute without authentication). Submitting orders via the CLOB requires an active wallet; however, data retrieval operations remain complimentary.
Is there a Python library for Polymarket?: Multiple community-developed Python packages are available on GitHub. Look for "polymarket-py" to identify the most actively maintained implementations.