Polymarket API Guide: Gamma, CLOB & Data API (2026)

Yes, Polymarket has an API — three of them, actually. Market data is completely free and requires no API key, no authentication, and no wallet. But the documentation is spread across three separate services with different base URLs, and figuring out which one you need is half the battle.

This guide covers all three Polymarket APIs, how they fit together, and working code to get you pulling live odds in under five minutes.

---

---

The Three Polymarket APIs at a Glance

Polymarket splits its API surface into three services:

API	Base URL	What it's for	Auth required
Gamma API	gamma-api.polymarket.com	Discovering events and markets, search, tags	None
CLOB API	clob.polymarket.com	Prices, order books, spreads, price history, trading	None for data; wallet auth for trading
Data API	data-api.polymarket.com	User positions, trade history, holders, open interest	None

The mental model: Gamma tells you what exists, CLOB tells you what it costs, Data tells you who's trading it.

---

---

Polymarket's Data Model: Events vs. Markets

Before you write any code, understand the two core objects:

• An event is a top-level question, like "Who will win the 2028 Presidential Election?" It contains one or more markets.
• A market is a specific tradable binary outcome within that event — e.g., "Will Gavin Newsom win?" Each market maps to a pair of CLOB token IDs (one for Yes, one for No).

A market's outcomes and outcomePrices arrays map 1:1, and prices are implied probabilities:

{
  "outcomes": "[\"Yes\", \"No\"]",
  "outcomePrices": "[\"0.20\", \"0.80\"]"
}

Index 0 means Yes is trading at 20¢ — a 20% implied probability. Note that both fields are JSON-encoded strings, not native arrays. You'll need to parse them (a common gotcha).

---

---

Gamma API: Finding Events and Markets

The Gamma API is where every integration starts. Key endpoints:

Endpoint	Description
GET /events	List events with filtering and pagination
GET /events/{id}	Single event by ID
GET /markets	List markets with filtering and pagination
GET /markets/{id}	Single market by ID
GET /public-search	Search events, markets, and profiles
GET /tags	Ranked tags/categories

No key needed:

curl "https://gamma-api.polymarket.com/events?limit=5&active=true&closed=false"

In Python:

import requests

resp = requests.get(
    "https://gamma-api.polymarket.com/events",
    params={"limit": 10, "active": "true", "closed": "false", "order": "volume", "ascending": "false"},
)
for event in resp.json():
    print(event["title"], "-", event.get("volume"))

---

---

CLOB API: Prices, Books, and History

Once you have a market's CLOB token ID, the CLOB API gives you live pricing:

Endpoint	Description
GET /price	Price for a single token
GET /prices	Prices for multiple tokens
GET /book	Order book for a token
POST /books	Order books for multiple tokens
GET /prices-history	Historical price data
GET /midpoint	Midpoint price
GET /spread	Bid/ask spread

import requests

token_id = "YOUR_CLOB_TOKEN_ID"  # from the market object's clobTokenIds field
book = requests.get("https://clob.polymarket.com/book", params={"token_id": token_id}).json()
print("Best bid:", book["bids"][0], "Best ask:", book["asks"][0])

A market is tradable via the CLOB when enableOrderBook is true on the market object.

---

---

Data API: Positions, Trades, and Whales

The Data API exposes on-chain activity:

Endpoint	Description
GET /positions?user={address}	Current positions for a wallet
GET /activity?user={address}	On-chain activity for a wallet
GET /trades	Trade history
GET /holders	Top holders of a market
GET /oi	Open interest

This is the raw feed behind "whale watching" — if you want pre-computed smart money signals instead of building wallet tracking from scratch, that's exactly what Prediction HuntPrediction.com's Smart Money feed and WebSocket channel provide.

---

---

Do You Need a Polymarket API Key?

For market data: no. All three read APIs are public.

For trading: yes, sort of. Placing orders through the CLOB requires wallet-based authentication — you derive API credentials from your Polygon wallet's private key using the official py-clob-client library, and you'll need USDC on Polygon with token allowances set. Trading is where most of the complexity (and most of the "polymarket api key" confusion) lives. See our Polymarket trading bot tutorial for the full walkthrough.

---

---

Polymarket API Rate Limits

Polymarket enforces per-endpoint rate limits that vary by service and can change — check the official docs for current numbers before going to production. Practical tips that hold regardless:

• Batch requests where endpoints support it (GET /prices, POST /books) instead of looping single calls.
• Use the WebSocket feed for live prices rather than polling REST.
• Cache Gamma metadata (event/market structure changes far less often than prices).

---

---

WebSockets: Streaming Instead of Polling

Polymarket offers a WebSocket service for real-time CLOB updates (order book changes, price updates, trades). For a bot or dashboard, streaming is strictly better than polling: lower latency, no rate limit pressure.

---

---

The Catch: Polymarket Is Only One Platform

Here's the thing about building on the Polymarket API directly — the moment you want context, you're integrating again. Is 42¢ for Trump on Polymarket a good price? You can't know without also checking Kalshi, PredictIt, and the rest. Each has its own API, auth scheme, data model, and naming conventions (presidential-2028 on Polymarket is PRES-2028-DEM on Kalshi is #8102 on PredictIt).

That's the problem the Prediction HuntPrediction.com API solves: one API, 6 platforms, with cross-platform entity resolution built in — the same event automatically matched across every platform:

curl -H "X-API-Key: YOUR_API_KEY" \
  "https://prediction.com/api/v2/search?q=presidential+election"

One call returns the same market's price on Polymarket, Kalshi, PredictIt, ProphetX, and more, so you can spot the best price (or an arbitrage gap) instantly. The free tier includes 1,000 requests/month with no credit card.

---

Want Polymarket, Kalshi, PredictIt, and 3 more platforms in a single API call? Get a free Prediction HuntPrediction.com API key — 1,000 requests/month, no credit card required.