Polymarket API Guide: Build Trading Bots & Analytics Tools

The Polymarket API provides programmatic access to one of the world's largest prediction markets. Whether you're building trading bots, analytics dashboards, or research tools, this comprehensive guide covers everything you need to know about integrating with Polymarket's API endpoints, authentication, rate limits, and best practices.

Understanding Polymarket's API Architecture

Polymarket operates a hybrid architecture that combines off-chain order matching with on-chain settlement. This design provides the speed of centralized exchanges while maintaining the security and transparency of blockchain-based systems.

API Components Overview

• REST API: For market data, order management, and account information
• WebSocket API: Real-time price feeds, order book updates, and trade notifications
• CLOB (Central Limit Order Book): The core trading engine that matches orders
• Gamma Markets API: Access to market metadata and resolution information

The API is built on Polygon blockchain infrastructure, using USDC as the settlement currency. All trades ultimately settle on-chain through smart contracts, ensuring transparency and immutability.

Getting Started: Authentication and Setup

API Key Generation

To access Polymarket's trading API, you'll need to generate API credentials. The process involves:

1. Connect Your Wallet: Link your Ethereum-compatible wallet to Polymarket
2. Enable API Access: Navigate to Settings → API and enable API trading
3. Generate Credentials: Create an API key and secret pair
4. Set Permissions: Configure read-only or full trading access
5. Secure Your Keys: Store credentials securely—never expose them in client-side code

Authentication Methods

Polymarket uses HMAC-SHA256 signature authentication for API requests. Each request must include:

• POLY_API_KEY: Your public API key in the request header
• POLY_SIGNATURE: HMAC-SHA256 signature of the request payload
• POLY_TIMESTAMP: Unix timestamp (requests expire after 30 seconds)
• POLY_PASSPHRASE: Optional additional security layer

Core API Endpoints

Market Data Endpoints

These endpoints provide read-only access to market information and don't require authentication:

GET /markets

Returns a list of all active markets with basic metadata including market ID, question, end date, and current prices.

GET /markets/{market_id}

Retrieves detailed information about a specific market including resolution source, rules, and historical data.

GET /markets/{market_id}/orderbook

Returns the current order book with bid and ask levels, depths, and spread information.

GET /markets/{market_id}/trades

Fetches recent trade history including price, size, timestamp, and trade direction.

Trading Endpoints

These endpoints require authentication and allow you to place and manage orders:

POST /orders

Creates a new order. Required parameters include market_id, side (buy/sell), outcome (yes/no), price, and size.

DELETE /orders/{order_id}

Cancels an open order. Returns confirmation of cancellation or error if order already filled.

GET /orders

Lists all your open orders with optional filtering by market, status, or date range.

GET /positions

Returns your current positions across all markets including entry price, current value, and unrealized P&L.

WebSocket API for Real-Time Data

For real-time market data and order updates, Polymarket provides WebSocket connections that push data instantly rather than requiring polling.

Available WebSocket Channels

• price: Real-time price updates for subscribed markets
• orderbook: Live order book changes with bid/ask updates
• trades: Stream of executed trades as they occur
• user: Private channel for order fills and position updates (authenticated)

WebSocket Connection Example

Connect to the WebSocket endpoint and subscribe to channels by sending JSON messages. The connection supports multiple simultaneous subscriptions and automatically handles reconnection on network issues.

Rate Limits and Best Practices

Rate Limit Tiers

Polymarket implements rate limiting to ensure fair access and system stability:

• Public Endpoints: 100 requests per minute per IP
• Authenticated Read: 300 requests per minute per API key
• Trading Endpoints: 60 orders per minute per API key
• WebSocket: 20 subscriptions per connection

Handling Rate Limits

When you exceed rate limits, the API returns HTTP 429 status codes. Best practices include:

• Implement exponential backoff when receiving 429 responses
• Use WebSocket streams instead of polling for real-time data
• Batch multiple market queries into single requests where possible
• Cache frequently accessed data locally with appropriate TTL

Building a Simple Trading Bot

Here's a high-level architecture for building a basic Polymarket trading bot:

Bot Architecture Components

1. Data Collector: WebSocket connection gathering real-time prices and order book data
2. Strategy Engine: Logic layer that analyzes data and generates trading signals
3. Order Manager: Handles order placement, tracking, and cancellation
4. Risk Manager: Enforces position limits, stop-losses, and exposure controls
5. Logger: Records all actions and outcomes for analysis and debugging

Common Bot Strategies

• Market Making: Provide liquidity by placing orders on both sides of the spread
• Arbitrage: Exploit price discrepancies across related markets
• Momentum: Follow price trends based on volume and velocity signals
• News Sentiment: React to news events using NLP analysis

Error Handling and Debugging

Common API Errors

• 400 Bad Request: Invalid parameters—check required fields and data types
• 401 Unauthorized: Invalid API credentials or expired signature
• 403 Forbidden: Insufficient permissions or geo-restricted access
• 404 Not Found: Market or order doesn't exist
• 429 Too Many Requests: Rate limit exceeded—implement backoff
• 500 Internal Error: Server-side issue—retry with exponential backoff

Debugging Tips

• Log all API requests and responses with timestamps
• Verify signature calculation matches expected format
• Check timestamp synchronization between your server and API
• Use test/sandbox environment when available for development

Advanced Integration Patterns

Building Analytics Dashboards

The API enables building sophisticated analytics tools. Common use cases include:

• Portfolio Tracking: Monitor positions and P&L in real-time
• Market Analysis: Track volume, liquidity, and price movements
• Whale Watching: Identify large trades and smart money flows
• Historical Analysis: Backtest strategies against past market data

Multi-Market Strategies

Advanced traders often work across multiple related markets. The API supports monitoring correlations between markets, identifying arbitrage opportunities, and building basket strategies across related outcomes.

Security Best Practices

• Secure Key Storage: Use environment variables or secret management services
• IP Whitelisting: Restrict API access to known server IPs when possible
• Minimal Permissions: Only enable trading permissions when necessary
• Regular Key Rotation: Periodically generate new API credentials
• Audit Logging: Monitor all API activity for unauthorized access
• Rate Limit Alerts: Set up notifications for unusual request patterns

For comprehensive platform security information, see our guide on Polymarket safety and security.

Community Resources and Support

• Official Documentation: docs.polymarket.com for complete API reference
• GitHub Repositories: Official SDKs and example implementations
• Discord Community: Active developer community for questions and support
• API Changelog: Stay updated on new features and breaking changes