Polymarket API Tutorial: Python Authentication, Orders & WebSocket Streaming (2026)

This tutorial walks you through the Polymarket API from first authentication to a working trading bot. You’ll set up py-clob-client-v2, authenticate with EIP-712, place orders, stream prices via WebSocket, and handle rate limits — all with tested Python code.

⚠️ CLOB V2 is live (April 28, 2026). Polymarket migrated its entire trading stack to CLOB V2 in a hard cutover: new Exchange contracts, a rewritten CLOB backend, new V2 SDK packages, a new order struct, a new fee model, pUSD collateral (replacing USDC.e), and a new builder-attribution mechanism. There is no backward compatibility — the V1 SDKs (py-clob-client, @polymarket/clob-client) and V1-signed orders stopped working on production at cutover. This guide has been updated for V2. Migrating from V1? See Polymarket’s Migrating to CLOB V2 guide.

Polymarket splits its functionality across three APIs (CLOB, Gamma, Data) plus WebSocket channels. This guide covers them all in the order you’ll need them. For a method-by-method SDK reference, see the py_clob_client Reference. For a side-by-side comparison of Polymarket and Kalshi endpoints, see the Prediction Market API Reference.

Last verified against Polymarket’s CLOB V2 API: May 2026. We update this guide whenever the API changes. Check the Polymarket Changelog for the latest updates.

Try it live: Test these endpoints instantly in the API Playground — no setup, no keys, real data in your browser.

Architecture Overview

Polymarket’s API isn’t one API — it’s three primary APIs plus a Bridge API and real-time streaming channels. Understanding this architecture is essential before writing any code.

Real-time streaming channels (not separate REST APIs):

Polymarket’s sports channel covers game scores and status, but not traditional odds formats. For comparing prediction market probabilities against sportsbook lines, see Offshore Sportsbook Odds Normalization and the Offshore Sportsbook API Guide.

Polymarket US: A separate CFTC-regulated API exists at api.polymarket.us with different auth (Ed25519), different SDKs, and KYC requirements. See the Polymarket US vs. Global API Guide for a complete comparison.

The mental model: Use the Gamma API to discover markets. Use the CLOB API to read prices and trade. Use the Data API to track positions and history. Use WebSockets for real-time updates.

How Polymarket Works Under the Hood

Before diving into endpoints, you need to understand the on-chain architecture because it affects how you interact with the API.

Polymarket runs on the Polygon blockchain. Markets use the Conditional Token Framework (CTF), an ERC-1155 standard where each market outcome is a tradable token. When you “buy YES” on a market, you’re actually acquiring YES outcome tokens.

The CLOB (Central Limit Order Book) is hybrid-decentralized: order matching happens off-chain for speed, but settlement happens on-chain for security. Orders are EIP-712 signed messages — you sign a structured order with your private key, and the operator matches it off-chain, then settles the swap on-chain via the Exchange contract. (CLOB V2 deployed new Exchange contracts and bumped the EIP-712 Exchange signing domain from version 1 to 2; the V2 SDKs handle this for you.)

Key implications for developers:

• You need a Polygon wallet (private key) to trade
• pUSD is the collateral asset (CLOB V2) — positions are denominated in pUSD (Polymarket USD), an ERC-20 on Polygon backed 1:1 by USDC. The polymarket.com UI wraps USDC.e → pUSD automatically (one-time approval); API-only traders must wrap USDC.e into pUSD via the Collateral Onramp contract’s wrap() function before trading. (Pre-V2, collateral was USDC.e directly.)
• Token IDs are critical — every market outcome has a unique token ID (not a ticker symbol)
• Prices range from 0.00 to 1.00 — representing the probability (and cost in USDC) of that outcome
• YES + NO prices should sum to ~$1.00 — any deviation is an arbitrage opportunity
• Tick sizes matter — most markets use 0.01 ticks, but some use 0.001

Getting Started: Your First API Call (No Auth Required)

The fastest way to start is reading public market data. No wallet, no keys, no authentication.

Fetch All Active Markets (Gamma API)

import requests

# Fetch open markets from the Gamma API
response = requests.get(
    "https://gamma-api.polymarket.com/markets",
    params={
        "closed": False,
        "limit": 10
    }
)

markets = response.json()

for market in markets:
    print(f"{market['question']}")
    print(f"  Token ID (YES): {market['clobTokenIds']}")
    print(f"  Outcome Prices: {market['outcomePrices']}")
    print(f"  Volume: ${float(market.get('volume', 0)):,.0f}")
    print()

Get a Price (CLOB API)

# Get the current price for a specific outcome token
token_id = "<your-token-id>"  # Get this from the Gamma API response

price = requests.get(
    f"https://clob.polymarket.com/price",
    params={
        "token_id": token_id,
        "side": "BUY"
    }
)

print(f"Current buy price: {price.json()['price']}")

Get the Order Book (CLOB API)

book = requests.get(
    f"https://clob.polymarket.com/book",
    params={"token_id": token_id}
)

data = book.json()
print(f"Best bid: {data['bids'][0]['price'] if data['bids'] else 'No bids'}")
print(f"Best ask: {data['asks'][0]['price'] if data['asks'] else 'No asks'}")
print(f"Midpoint: {data.get('mid', 'N/A')}")

Authentication

Public endpoints (prices, order books, market listings) require no authentication. Trading endpoints (placing orders, canceling orders, checking your positions) require EIP-712 signed requests.

How Authentication Works

1. You have a private key — from an EOA (MetaMask), a deposit wallet (POLY_1271), an email/Magic proxy, or a Gnosis Safe
2. You derive API credentials — the client library generates a key/secret pair from your wallet signature
3. You sign each trading request — using five L2 headers: POLY_ADDRESS, POLY_SIGNATURE, POLY_TIMESTAMP, POLY_API_KEY, and POLY_PASSPHRASE

Auth issues? See our Polymarket Auth Troubleshooting Guide for common error codes (INVALID_SIGNATURE, NONCE_ALREADY_USED, clock drift) and step-by-step fixes.

Wallet Types and Signature Types

CLOB V2 supports four signature types. New API users should use a deposit wallet with POLY_1271 (type 3) — Polymarket now steers new integrations there rather than the older Safe/proxy flows. Existing Safe and proxy users are unaffected and can keep their current type.

The funder address is the actual address holding your funds on Polymarket. When using proxy or deposit wallets, the signing key differs from the funded address.

Python Authentication Setup

from py_clob_client_v2 import ClobClient  # V2 package — import is py_clob_client_v2

HOST = "https://clob.polymarket.com"
CHAIN_ID = 137  # Polygon mainnet

# Recommended for new API users — deposit wallet (POLY_1271, signature_type=3):
client = ClobClient(
    host=HOST,
    chain_id=CHAIN_ID,
    key="<your-private-key>",
    signature_type=3,
    funder="<your-deposit-wallet-address>"
)

# EOA (MetaMask) users (funder is the EOA itself):
client = ClobClient(host=HOST, chain_id=CHAIN_ID, key="<your-private-key>")

# Derive and set API credentials (do this once, then reuse).
# V2 renamed this method: create_or_derive_api_creds() -> create_or_derive_api_key()
client.set_api_creds(client.create_or_derive_api_key())

TypeScript Authentication Setup

import { ClobClient, Side } from "@polymarket/clob-client-v2";

// V2 takes a single options object, uses `chain` (not `chainId`), and a viem signer.
const client = new ClobClient({
    host: "https://clob.polymarket.com",
    chain: 137,          // Polygon — note `chain`, not `chainId`
    signer,              // viem account (V2 uses viem, not ethers.js)
    signatureType: 3,    // POLY_1271 deposit wallet (recommended for new users)
    funder: "<your-deposit-wallet-address>",
});

// Derive API credentials once, then attach them (V2 method name):
const creds = await client.createOrDeriveApiKey();
client.setApiCreds(creds);

Rust Authentication Setup

// V2 crate: polymarket_client_sdk_v2  (cargo add polymarket_client_sdk_v2 --features clob)
use polymarket_client_sdk_v2::clob::{Client, Config};
use alloy::signers::local::LocalSigner;
use std::str::FromStr;

let private_key = std::env::var("PRIVATE_KEY").expect("Need a private key");
let signer = LocalSigner::from_str(&private_key)?
    .with_chain_id(Some(137));

let client = Client::new("https://clob.polymarket.com", Config::default())?
    .authentication_builder(&signer)
    .authenticate()
    .await?;

The V2 Rust client (rs-clob-client-v2) is the newest of the three SDKs. Check the repository for the current builder API — method names may differ from the example above.

Token Allowances (EOA Users Only)

If you’re using a direct EOA wallet (not a proxy), you must approve the Exchange contracts before trading:

# Approve pUSD and conditional tokens for the V2 Exchange contracts.
# (EOA only — proxy and deposit wallets handle approvals for you.)
# This only needs to be done once per wallet.
# See: https://docs.polymarket.com/v2-migration

Proxy and deposit-wallet users (email/Magic, Gnosis Safe, or POLY_1271) do not need to set allowances — the proxy or deposit contract handles this.

CLOB API Reference

The CLOB API is the core trading interface. It handles prices, order books, and order management.

Public Endpoints (No Auth)

GET /price

Returns the current price for a token.

GET https://clob.polymarket.com/price?token_id=<id>&side=BUY

Parameters:

• token_id (required) — The outcome token ID
• side (required) — BUY or SELL

Example response:

{
  "price": "0.567"
}

Try /price live in the API Playground →

GET /midpoint

Returns the midpoint between best bid and best ask.

GET https://clob.polymarket.com/midpoint?token_id=<id>

Example response:

{
  "mid": "0.5650"
}

Try /midpoint live in the API Playground →

GET /book

Returns the full order book for a token.

GET https://clob.polymarket.com/book?token_id=<id>

Response includes bids, asks, and a few trading parameters. The get-book/get-books endpoints return min_order_size, neg_risk, and tick_size inline (added July 2025) — convenient so you don’t need a separate lookup just for a market’s tick size or neg-risk flag. For market context (question text, slug, end date, outcome labels, status) you still use the Gamma API, the new_market WebSocket event, or getClobMarketInfo.

Example response (truncated):

{
  "market": "0x...",
  "asset_id": "21742633143463906290569050155826241533067272736897614950488156847949938836455",
  "bids": [
    {"price": "0.56", "size": "1250.00"},
    {"price": "0.55", "size": "3400.00"}
  ],
  "asks": [
    {"price": "0.57", "size": "800.00"},
    {"price": "0.58", "size": "2100.00"}
  ],
  "mid": "0.5650",
  "spread": "0.01",
  "hash": "0x..."
}

Try /book live in the API Playground →

POST /books

Batch endpoint — fetch order books for multiple tokens in one request. It’s a POST (the token list goes in the request body), not a GET. Polymarket also exposes batch POST pricing variants: /prices, /midpoints, /spreads, and last-trade-price endpoints.

from py_clob_client_v2.clob_types import BookParams

books = client.get_order_books([
    BookParams(token_id="<token-id-1>"),
    BookParams(token_id="<token-id-2>"),
])

Authenticated Endpoints (Trading)

All trading endpoints require L2 authentication headers.

POST /order — Place a Single Order

All orders on Polymarket are limit orders. Market orders are simulated by setting a marketable price against resting liquidity.

Order types:

• GTC (Good Til Cancelled) — Rests on the book until filled or cancelled
• FOK (Fill or Kill) — Must execute immediately and completely, or is rejected entirely
• FAK (Fill and Kill) — Fills whatever is available immediately, cancels the rest

CLOB V2 order struct & fees: The signed order no longer carries nonce, feeRateBps, or taker. V2 adds timestamp (in ms — it now provides per-address order uniqueness, replacing nonce), metadata, and builder. Fees are no longer embedded in the order — the protocol sets them at match time and the SDK handles the math, so don’t try to set feeRateBps yourself. For market buys, the optional userUSDCBalance field lets the SDK compute fee-adjusted fill amounts. If you sign orders manually, the EIP-712 Exchange domain version is now 2 (the ClobAuth domain stays 1) with new V2 verifyingContract addresses.

Place a limit order (Python):

from py_clob_client_v2.clob_types import OrderArgs, OrderType
from py_clob_client_v2.order_builder.constants import BUY

order = OrderArgs(
    token_id="<token-id>",
    price=0.50,       # Price in USDC (0.00 to 1.00)
    size=10.0,        # Number of shares
    side=BUY
)

signed = client.create_order(order)
response = client.post_order(signed, OrderType.GTC)
print(response)

Place a market order (Python):

from py_clob_client_v2.clob_types import MarketOrderArgs, OrderType
from py_clob_client_v2.order_builder.constants import BUY

market_order = MarketOrderArgs(
    token_id="<token-id>",
    amount=25.0,       # Dollar amount to spend
    side=BUY,
    order_type=OrderType.FOK
)

signed = client.create_market_order(market_order)
response = client.post_order(signed, OrderType.FOK)

Place a limit order (TypeScript):

const order = await client.createAndPostOrder(
    {
        tokenID: "<token-id>",
        price: 0.50,
        size: 10,
        side: Side.BUY
    },
    {
        tickSize: "0.01",
        negRisk: false  // true for neg-risk markets
    }
);

Post-only orders:

The postOnly flag ensures your order is added to the book as a maker order. If it would immediately match (cross the spread), it’s rejected instead of executed. This is critical for market-making strategies where you only want to earn the maker rebate.

order = OrderArgs(
    token_id="<token-id>",
    price=0.48,
    size=100.0,
    side=BUY
)

signed = client.create_order(order)
# postOnly cannot be combined with FOK or FAK
response = client.post_order(signed, OrderType.GTC, post_only=True)

Example response:

{
  "orderID": "0xabc123...",
  "status": "live",
  "transactionsHashes": []
}

Possible status values: live (resting on book), matched (fully filled), delayed (pending matching engine processing).

POST /orders — Batch Orders

Place up to 15 orders in a single request. Essential for market makers updating multiple price levels.

orders = []
for price in [0.48, 0.49, 0.50]:
    order = OrderArgs(
        token_id="<token-id>",
        price=price,
        size=50.0,
        side=BUY
    )
    orders.append(client.create_order(order))

response = client.post_orders(orders, OrderType.GTC)

The batch limit was increased from 5 to 15 orders per call in 2025.

DELETE /order — Cancel a Single Order

response = client.cancel(order_id="<order-id>")

DELETE /orders — Cancel All Orders

response = client.cancel_all()

Gamma API Reference

The Gamma API is your market discovery layer. Use it to find markets, get metadata, and understand the structure of events.

Understanding Gamma’s Data Model

Polymarket organizes data hierarchically:

Series (e.g., "US Presidential Election")
  └── Event (e.g., "2028 Presidential Election Winner")
       └── Market (e.g., "Will Kamala Harris win?")
            └── Outcomes (YES / NO, each with a token ID)

Key Endpoints

GET /events — List Events

GET https://gamma-api.polymarket.com/events?closed=false&limit=20

Returns events with their associated markets. Each event can contain multiple markets.

GET /markets — List Markets

GET https://gamma-api.polymarket.com/markets?closed=false&limit=50

Key fields in the response:

• question — The human-readable market question
• clobTokenIds — Array of token IDs for each outcome (critical for trading)
• outcomePrices — Current prices as a JSON string
• volume — Total trading volume in USDC
• liquidity — Current available liquidity
• endDate — When the market resolves
• conditionId — The on-chain condition identifier
• slug — URL-friendly market identifier

Note (April 9, 2026): GET /markets now defaults closed=false, so passing closed=false explicitly is no longer required (though still fine). Pass closed=true to fetch resolved markets instead.

Keyset (Cursor) Pagination

For large pulls, prefer the keyset endpoints added April 10, 2026: GET /markets/keyset and GET /events/keyset. They use opaque cursor tokens instead of offset:

GET https://gamma-api.polymarket.com/markets/keyset?limit=100&after_cursor=<token>

The response wraps results with a next_cursor:

{ "markets": [ ... ], "next_cursor": "eyJpZCI6..." }

Pass next_cursor back as after_cursor to page forward. The maximum limit is 100 (capped May 14, 2026). The offset-based GET /markets / GET /events still work but will be deprecated, so build new pagination on keyset.

GET /events/{id} — Get Event Details

GET https://gamma-api.polymarket.com/events/<event-id>

Returns full event details including all child markets.

GET /markets?tag= — Filter by Category

Polymarket tags markets with categories. Common tags: politics, crypto, sports, science, pop-culture.

# Get all sports markets
response = requests.get(
    "https://gamma-api.polymarket.com/markets",
    params={"tag": "sports", "closed": False}
)

Sports-Specific Endpoints

Polymarket has dedicated sports endpoints for structured sports market data:

GET https://gamma-api.polymarket.com/sports

Data API Reference

The Data API provides user-specific and aggregate analytics data.

Base URL: https://data-api.polymarket.com

Key Endpoints

GET /positions — User Positions

Returns current positions for a wallet address, including token balances and unrealized P&L.

GET /activity — User Activity

Returns trade history, deposits, withdrawals.

GET /trades — Trade History

Historical trade data for analysis and backtesting.

The Data API is fully public and requires no authentication. You can query any wallet’s positions and activity.

Newer Data API endpoints worth knowing: open interest, top holders, closed positions, total position value, the builder leaderboard / daily volume (both now include builderCode as of May 18, 2026), the trader leaderboard, and an accounting-snapshot ZIP export.

Other Useful Endpoints

A few endpoints that round out an agent’s toolkit:

• GET /clob-market-info (getClobMarketInfo) — tick size, min order size, fee details (fd), tokens, and RFQ flag in a single call.
• GET /fee-rate and GET /tick-size — read those parameters directly.
• POST /heartbeat — the HeartBeats endpoint for auto-cancel-on-disconnect (see the WebSocket section).
• DELETE /cancel-market-orders — cancel every open order for one market.
• GET /server-time — check clock drift before signing (EIP-712 timestamps are drift-sensitive).
• Sports (structured): GET /sports metadata, valid sports market types, and team listings.

Bridge API

The Bridge API at https://bridge.polymarket.com handles deposits and withdrawals. It proxies fun.xyz infrastructure for cross-chain bridging.

POST /withdraw

Creates withdrawal (bridge deposit) addresses for moving funds off Polygon to a supported chain. It takes no amount and requires no auth — you call it to get deposit addresses, then send funds to the returned address. The request body uses address (your source Polygon wallet), toChainId (the destination chain ID as a numeric string, e.g. "1" for Ethereum or "8453" for Base), toTokenAddress (the destination token contract address), and recipientAddr:

curl -X POST https://bridge.polymarket.com/withdraw \
  -H 'Content-Type: application/json' \
  -d '{
    "address": "0x...source-polygon-wallet",
    "toChainId": "1",
    "toTokenAddress": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    "recipientAddr": "0x...destination"
  }'

The response returns multi-chain deposit addresses:

{
  "address": {
    "evm": "0x23566f8b2E82aDfCf01846E54899d110e97AC053",
    "svm": "CrvTBvzryYxBHbWu2TiQpcqD5M7Le7iBKzVmEj3f36Jb",
    "btc": "bc1q8eau83qffxcj8ht4hsjdza3lha9r3egfqysj3g"
  }
}

Companion Bridge endpoints include GET /supported-assets, address-creation POSTs, POST /quote, and transaction-status lookups. Multi-chain support covers EVM, Solana, and Bitcoin. The Bridge general rate limit is 50/10s. Check the Polymarket Changelog for the full list of supported chains and tokens.

WebSocket API

For real-time applications — trading bots, live dashboards, arbitrage systems — the WebSocket API is essential. Polymarket offers four WebSocket channels:

Market Channel (Public)

Orderbook updates, price changes, trade data, and custom events (best_bid_ask, new_market, market_resolved when custom_feature_enabled: true).

import asyncio
import websockets
import json

async def stream_prices():
    uri = "wss://ws-subscriptions-clob.polymarket.com/ws/market"

    async with websockets.connect(uri) as ws:
        await ws.send(json.dumps({
            "assets_ids": ["<token-id>"],
            "type": "market",
            "custom_feature_enabled": True
        }))

        async def heartbeat():
            while True:
                await asyncio.sleep(10)
                await ws.send("PING")

        asyncio.create_task(heartbeat())

        async for message in ws:
            if message == "PONG":
                continue
            data = json.loads(message)
            print(f"Update: {data}")

asyncio.run(stream_prices())

User Channel (Authenticated)

Real-time order status updates — fills, cancellations, status changes. Requires API key/secret/passphrase in the subscription payload. Subscribes by condition ID (not asset ID).

Sports Channel

Streams live game scores, periods, and status for all active sports events. No subscription message needed — connections receive all active events automatically.

RTDS (Real-Time Data Socket)

Low-latency stream for crypto prices (from Binance and Chainlink sources) and platform comments. Supports topic-based subscriptions with optional filters.

WebSocket connections do not count against REST API rate limits. Using WebSockets instead of polling is the most effective way to avoid 429 errors.

HeartBeats API (January 2026): Polymarket added a dedicated HeartBeats API endpoint for connection health monitoring and automatic order cancellation on disconnect. If your bot holds open orders over a long WebSocket session, wiring this in protects you from stranded orders during transient network drops. See the Polymarket Changelog for the endpoint spec.

Deep dive: For complete channel documentation, subscription formats, orderbook reconstruction, and production reconnection patterns, see the Polymarket WebSocket & Orderbook Guide.

Rate Limits

Polymarket publishes concrete rate limits enforced via Cloudflare throttling. When limits are exceeded, requests are delayed/queued rather than immediately rejected. CLOB trading limits were raised on April 8, 2026 — current values below.

CLOB trading endpoints carry dual burst (per 10s) + sustained (per 10 min) limits:

Every response includes X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset headers.

Basic retry pattern:

import time
import random

def retry_on_429(func, *args, max_retries=3, **kwargs):
    for attempt in range(max_retries):
        try:
            return func(*args, **kwargs)
        except Exception as e:
            if "429" in str(e) and attempt < max_retries - 1:
                delay = 2 ** attempt + random.uniform(0, 1)
                time.sleep(delay)
            else:
                raise

If you’re hitting rate limits frequently:

1. Use WebSockets instead of polling for real-time data
2. Batch order operations — POST /orders handles up to 15 orders in one request
3. Cache Gamma API responses — market metadata changes infrequently
4. Apply for the Market Maker program for elevated limits

Full rate limits reference: See our Polymarket Rate Limits Guide for complete header documentation, retry code in Python and TypeScript, and strategies for staying within limits.

Key Concepts for Agent Builders

Finding Token IDs

Every market outcome has a unique token ID. This is the primary identifier you’ll use for all trading operations. You get token IDs from the Gamma API:

response = requests.get(
    "https://gamma-api.polymarket.com/markets",
    params={"slug": "will-bitcoin-hit-100k-by-2026"}
)

market = response.json()[0]
token_ids = market["clobTokenIds"]  # [YES_token_id, NO_token_id]

Understanding Neg-Risk Markets

Some Polymarket markets use a “negative risk” model where multiple outcomes share a single collateral pool. This is common in multi-outcome markets (e.g., “Who will win the election?” with 5+ candidates). When trading neg-risk markets, you need to set negRisk: true in your order parameters.

Common gotcha: Forgetting negRisk: true on neg-risk markets causes three distinct failures: (1) your order is rejected with a cryptic error because the Exchange contract doesn’t match, (2) split/merge operations fail because the CTF framework routes to the wrong contract, and (3) fee calculations are wrong because neg-risk markets use a different fee structure. Always check the market’s neg_risk field from the Gamma API before placing orders.

To check programmatically:

market = requests.get(
    "https://gamma-api.polymarket.com/markets",
    params={"slug": "your-market-slug"}
).json()[0]

is_neg_risk = market.get("negRisk", False)
# Pass this to your order builder

Inventory Management: Split and Merge

The Conditional Token Framework allows you to:

• Split USDC into YES + NO token pairs
• Merge YES + NO tokens back into USDC
• Redeem winning tokens after market resolution

This is essential for market makers managing inventory across both sides of a market.

# Splitting: 1 USDC → 1 YES token + 1 NO token
# Merging: 1 YES token + 1 NO token → 1 USDC
# Redeem: 1 winning token → 1 USDC (after resolution)

Fees

Polymarket fees are applied symmetrically on output assets (proceeds), and in CLOB V2 they are not embedded in your signed order — the protocol computes them at match time. The per-trade fee follows:

fee = C × feeRate × p × (1 − p)

where C is the number of shares and p is the share price. Since p × (1 − p) peaks at p = 0.5, the maximum effective rate for a category is feeRate × 0.25.

• Maker fees: 0% on all markets — limit orders that add liquidity are free.

• Taker fees: Set per category by feeRate (effective March 30, 2026). Peak rates (at p = 0.5):

  Category	feeRate	Peak rate
  Crypto	0.07	1.75%
  Economics / Culture / Weather / Other	0.05	1.25%
  Finance / Politics / Tech / Mentions	0.04	1.00%
  Sports	0.03	0.75%
  Geopolitics	0	fee-free

• Maker rebates: Calculated per-market — makers compete with other makers in the same market for rebates funded by taker fees. As of March 17, 2026, orders must remain on the book for a minimum of 3.5 seconds of active time to qualify for liquidity rewards. Takers can also earn a portion of fees back through the tiered Taker Rebate Program.

• Gas fees: Minimal on Polygon (fractions of a cent per transaction).

Reading fees programmatically: Call getClobMarketInfo(conditionID) — it returns fd = { r: feeRate, e: exponent, to: takerOnly } along with tick size, min order size, and the token IDs. Check the market’s feesEnabled boolean to know whether a market charges fees at all. (The Gamma feeSchedule object, added March 31, 2026, is also available, but getClobMarketInfo is the canonical V2 source.) Read live values rather than hardcoding the table above — category fees can shift.

Check the Polymarket Changelog for the latest fee schedule and the Builder Program for current maker rebate rates.

Builder Program & Relayer Client

If you’re building a consumer-facing application on top of Polymarket (not just a personal bot), the Builder Program provides higher rate limits, volume-based rewards, and access to the Relayer Client for gasless transactions. The program has tiered levels based on volume contributed.

Builder attribution (CLOB V2): Order attribution no longer uses HMAC-signed POLY_BUILDER_* headers (the separate builder-signing SDK is gone). Instead, copy your public builderCode (a bytes32 identifier) from Settings → Builder and attach it to each order via the builderCode field (or set it once at client construction). builderCode is a public identifier — it appears on-chain and on the builder leaderboard.

Relayer Client enables gasless order submission — your users don’t need POL for gas fees. Orders are submitted to the Relayer, which sponsors the gas and submits them on-chain. The HMAC builder API key (key/secret/passphrase, from onboarding at builders.polymarket.com) is still used to authenticate with the Relayer — only per-order attribution moved to builderCode.

SDK packages (unchanged in V2):

Python setup:

from py_builder_relayer_client import BuilderRelayerClient

relayer = BuilderRelayerClient(
    key="<your-builder-api-key>",
    secret="<your-builder-api-secret>",
    passphrase="<your-builder-passphrase>",
)

# As of April 21, 2026, POST /submit returns immediately with a transaction ID
# and state — transactionHash was removed. Poll GET /transaction for the hash.
submission = relayer.submit_order(signed_order)
# -> { "transactionID": "...", "state": "STATE_NEW" }
tx_id = submission["transactionID"]

See the Builder Program docs for onboarding, tier details, and the full Relayer API reference.

Official SDK Libraries

Looking for a complete method reference? See our py_clob_client Method Reference for every method with parameters, return types, and working code examples.

Polymarket maintains official CLOB V2 client libraries. The old V1 packages (py-clob-client, @polymarket/clob-client, polymarket-client-sdk) only work against the retired V1 backend — use the -v2 packages below.

The TypeScript V2 client uses viem for signing (not ethers.js) — install it alongside. Polymarket has also signaled a future unified SDK (Gamma + Data + CLOB in one package); until that lands, the -v2 CLOB clients above are current.

Community alternative: The polymarket-apis package is a third-party unified wrapper around CLOB, Gamma, Data, Web3, WebSocket, and GraphQL clients with Pydantic validation. Check its current version and confirm CLOB V2 compatibility before relying on it for trading — community wrappers can lag the official V2 packages. Install with pip install polymarket-apis.

Install

# Python
pip install py-clob-client-v2

# TypeScript (viem is a peer dependency in V2)
npm install @polymarket/clob-client-v2 viem

# Rust
cargo add polymarket_client_sdk_v2 --features clob

Version note: Always install the latest -v2 packages — the V1 packages and V1-signed orders no longer work on production. If you hit a breaking change, let us know on Twitter.

Putting It Together: A Minimal Trading Agent

Here’s a complete Python example that finds a market, checks the price, and places an order:

import requests
from py_clob_client_v2 import ClobClient
from py_clob_client_v2.clob_types import OrderArgs, OrderType
from py_clob_client_v2.order_builder.constants import BUY

# 1. Initialize authenticated client (POLY_1271 deposit wallet, signature_type=3 — recommended for new users)
client = ClobClient(
    host="https://clob.polymarket.com",
    chain_id=137,
    key="<your-private-key>",
    signature_type=3,
    funder="<your-deposit-wallet-address>"
)
client.set_api_creds(client.create_or_derive_api_key())

# 2. Discover a market via the Gamma API
markets = requests.get(
    "https://gamma-api.polymarket.com/markets",
    params={"closed": False, "limit": 5, "order": "volume", "ascending": False}
).json()

target = markets[0]
token_id = target["clobTokenIds"][0]  # YES token
print(f"Market: {target['question']}")
print(f"Current price: {target['outcomePrices']}")

# 3. Check the order book
book = client.get_order_book(token_id)
best_ask = float(book["asks"][0]["price"]) if book["asks"] else None
print(f"Best ask: {best_ask}")

# 4. Place a limit order below the current ask
if best_ask and best_ask > 0.05:
    my_price = round(best_ask - 0.02, 2)
    order = OrderArgs(
        token_id=token_id,
        price=my_price,
        size=10.0,
        side=BUY
    )
    signed = client.create_order(order)
    result = client.post_order(signed, OrderType.GTC)
    print(f"Order placed: {result}")

Common Patterns

Pattern 1: Price Monitoring Bot

Poll prices at an interval and trigger actions on threshold changes.

import time

def monitor_market(token_id, threshold_low, threshold_high):
    while True:
        mid = client.get_midpoint(token_id)
        price = float(mid)

        if price < threshold_low:
            print(f"ALERT: Price dropped to {price} — buying opportunity")
            # Place buy order logic here

        if price > threshold_high:
            print(f"ALERT: Price rose to {price} — selling opportunity")
            # Place sell order logic here

        time.sleep(5)  # Check every 5 seconds

Pattern 2: Cross-Market Arbitrage Scanner

Check if YES + NO prices deviate from $1.00 across markets.

def scan_arb_opportunities():
    markets = requests.get(
        "https://gamma-api.polymarket.com/markets",
        params={"closed": False, "limit": 100}
    ).json()

    for market in markets:
        prices = market.get("outcomePrices")
        if prices:
            try:
                parsed = [float(p) for p in prices.strip("[]").split(",")]
                total = sum(parsed)
                if total < 0.98 or total > 1.02:
                    print(f"ARB: {market['question']}")
                    print(f"  Prices sum to: {total:.4f}")
                    print(f"  Gap: {abs(1.0 - total):.4f}")
            except (ValueError, IndexError):
                continue

For agents scanning beyond prediction markets, the same arbitrage logic applies to sportsbook lines. Offshore sportsbooks like BetOnline and Bovada frequently price sports events differently from Polymarket — and the API access patterns differ significantly. See the Sports Betting Arbitrage Bot Guide for a full cross-platform implementation, and Offshore vs. Regulated Sportsbooks for a comparison of data access across both worlds.

Pattern 3: WebSocket + LLM Agent

Stream market updates and feed them to an LLM for analysis.

import asyncio
import websockets
import json

async def agent_loop():
    uri = "wss://ws-subscriptions-clob.polymarket.com/ws/market"

    async with websockets.connect(uri) as ws:
        # Subscribe to all watched markets in the initial message
        await ws.send(json.dumps({
            "assets_ids": watched_tokens,   # list of token IDs
            "type": "market"
        }))

        # To add/drop tokens later, send an operation message:
        # await ws.send(json.dumps({"operation": "subscribe", "assets_ids": ["<id>"]}))

        async for message in ws:
            if message == "PONG":
                continue
            data = json.loads(message)
            # Feed price update to your LLM/agent for analysis
            # agent.analyze(data)
            # If the agent recommends a trade, execute via CLOB API

Security Considerations

Building autonomous agents that handle real money demands careful security practices. See our Security Best Practices for Agent Betting guide for the full treatment. Key points:

• Never hardcode private keys — use environment variables or a secrets manager
• Use spending limits — configure your wallet with maximum position sizes
• Implement kill switches — your bot should have a way to cancel all orders and stop trading instantly
• Guard against prompt injection — if using LLMs, sanitize all market data before feeding it to the model
• Test on small amounts first — Polymarket has no demo/testnet environment, so start with minimal positions
• Monitor the heartbeat — the Rust SDK supports automatic heartbeats that cancel all orders if your client disconnects

Troubleshooting

For an in-depth breakdown of the 10 most common integration failures — including L1/L2 auth confusion, wallet type mismatches, identifier confusion, heartbeat timeouts, and US NO-side pricing — see the top 10 Polymarket API problems guide.

Order Rejected Errors

The CLOB matching engine rejects orders that violate market constraints. Common causes:

• Check that your price aligns with the market’s tick size (usually 0.01, but some markets use 0.001 — check the /book response for the min_tick_size field)
• Ensure you have sufficient pUSD balance on Polygon (CLOB V2 collateral; wrap USDC.e via the Collateral Onramp)
• For EOA wallets, verify token allowances are set for both the Exchange and Neg Risk Exchange contracts
• If using postOnly, your order may be crossing the spread — lower your bid or raise your ask
• Orders with size below the market minimum (typically 1.0 shares) are silently rejected

Authentication Failures (401 / INVALID_SIGNATURE)

Auth errors almost always come down to a mismatch between your wallet type and the signature parameters you’re sending.

• Verify your signature_type matches your wallet type: 0 for EOA, 1 for email/Magic proxy, 2 for Gnosis Safe, 3 for POLY_1271 deposit wallets (recommended for new API users)
• Ensure the funder address is correct for proxy wallets — this is the address holding funds, not the signing key address
• API credentials may need to be re-derived if you get persistent 401 errors — call client.create_or_derive_api_key() again
• Check for clock drift — EIP-712 signatures include a timestamp, and a drift of more than 60 seconds causes rejection
• See the full Polymarket Auth Troubleshooting Guide for error code reference

Rate Limit Errors (429)

When you hit rate limits, Polymarket’s Cloudflare layer queues your requests rather than immediately rejecting them — but sustained overuse will eventually return 429s.

• Switch from polling to WebSockets for real-time data — WebSocket connections do not count against REST rate limits
• Batch order operations using the POST /orders endpoint (up to 15 orders per call)
• Cache Gamma API responses — market metadata (questions, token IDs, slugs) changes infrequently
• Check X-RateLimit-Remaining headers before making bursts of requests
• See the Polymarket Rate Limits Guide for the full per-endpoint breakdown

Missing or Wrong Token IDs

Token ID confusion is the single most common issue for new Polymarket developers.

• Token IDs come from the Gamma API, not the CLOB API — use the clobTokenIds field from GET /markets
• clobTokenIds is an array: index 0 is typically YES, index 1 is NO, but always verify against outcomes
• Some multi-outcome (neg-risk) markets have their token IDs in a nested structure within the event response
• Token IDs are long numeric strings (not hex addresses) — e.g., 21742633143463906290569050155826241533067272736897614950488156847949938836455
• If a token ID returns empty order books, the market may have been resolved or delisted — check closed status via Gamma

What’s New in Official Docs

Polymarket’s official documentation has expanded significantly. Key areas now covered:

• CLOB V2 (April 28, 2026) — A hard-cutover upgrade of the entire trading stack: new Exchange contracts, V2 SDK packages, a new order struct, protocol-set fees, and pUSD collateral. V1 SDKs and V1-signed orders no longer work — see Migrating to CLOB V2
• pUSD collateral — Collateral migrated from USDC.e to pUSD (an ERC-20 backed 1:1 by USDC); API-only traders wrap via the Collateral Onramp
• Deposit wallets / POLY_1271 (type 3) — A new signature type now recommended for new API users
• Rate-limit increase (April 8, 2026) — CLOB trading burst/sustained limits raised (e.g., POST /order to 5,000/10s + 48,000/10min)
• Keyset pagination (April 10, 2026) — GET /markets/keyset & /events/keyset with cursor tokens; max limit capped at 100 (May 14, 2026)
• Relayer /submit change (April 21, 2026) — Returns { transactionID, state } immediately; poll GET /transaction for the on-chain hash
• builderCode attribution (May 18, 2026) — Per-order builder attribution via a public builderCode, now shown on the builder leaderboard
• GET /markets default changed (April 2026) — The closed query parameter now defaults to false, so most market discovery calls no longer need to pass it explicitly
• Programmatic fees — Read per-market fees via getClobMarketInfo() (canonical V2 source) or the Gamma feeSchedule object; check the feesEnabled flag
• Liquidity reward floor (March 2026) — Orders must sit on the book for at least 3.5 seconds to count toward liquidity rewards
• Multi-chain withdrawals (January 2026) — POST /withdraw now supports Solana and Bitcoin destinations in addition to EVM chains
• Fees and maker rebates — Per-market fee tiers, taker fees on crypto/sports markets, and per-market rebate calculation
• CTF operations — Split, merge, and redeem operations for conditional tokens
• Bridge flows — Deposit and withdrawal documentation via the Bridge API, including the new /withdraw endpoint for cross-chain bridging
• Resolution process — How markets resolve via the UMA oracle
• Market Maker program — Setup, trading requirements, liquidity rewards, and data feeds
• Builder Program — Tiers, profile setup, API keys, order attribution, and relayer client
• Order book parameters — get-book/get-books return min_order_size, neg_risk, and tick_size inline (not full market metadata — use Gamma or getClobMarketInfo for question/slug/dates)
• Subscription limits removed — The 100-token subscription limit on the Markets WebSocket channel has been removed; you can subscribe to unlimited token IDs
• Agent Skills — Polymarket published agent-skills on GitHub, a structured skill pack for AI agents covering auth, orders, WebSocket, CTF, bridge, and gasless transactions

AgentBets guides complement these official docs by providing implementation depth, cross-platform context, and agent-first patterns.

Changelog

Official Resources

• Polymarket Documentation
• Polymarket Changelog
• Polymarket Agent Skills — Structured skill pack for AI agents
• Python SDK (py-clob-client-v2)
• TypeScript SDK (clob-client-v2)
• Rust SDK (rs-clob-client-v2)
• Builder Relayer Client (Python)
• Builder Relayer Client (TypeScript)
• polymarket-apis (Community) — Unified third-party wrapper
• Polymarket Agents Framework — Official AI agent toolkit
• Discord Community

AgentBets Guides

• Build a Polymarket Trading Bot — From market scanning to production deployment
• Dome vs pmxt vs OddsPapi — Unified prediction market API comparison
• Polymarket WebSocket & Orderbook Guide — All four channels, orderbook reconstruction
• Polymarket Auth Troubleshooting — POLY headers, signatureType, error reference
• Polymarket TypeScript SDK Reference — @polymarket/clob-client methods with examples
• Polymarket Rust SDK Reference — Cargo setup, methods, and error handling
• Polymarket Gamma API Deep Dive — Market discovery, price history, backtesting
• Polymarket Subgraph Guide — On-chain data via GraphQL
• Polymarket US vs. Global API — Dual-stack architecture comparison
• Offshore Sportsbook API Guide — Data access for BetOnline, Bovada, and more
• Sports Betting vs Prediction Markets — When to use each

Frequently Asked Questions

How do I check my balance with py_clob_client?

Use client.get_balance_allowance() to get your pUSD balance plus token allowance info. (CLOB V2 migrated collateral from USDC.e to pUSD.) See our complete method reference for full examples with response structures.

What are Polymarket’s API rate limits?

Polymarket publishes concrete rate limits enforced via Cloudflare throttling. The general limit is 15,000 requests per 10 seconds, with specific limits per endpoint (e.g., POST /order allows 5,000/10s burst and 48,000/10min sustained, raised April 8, 2026). See our Rate Limits Guide for the full per-endpoint table and retry code.

How do I get my positions using py_clob_client?

Positions come from the Data API, not the CLOB client — query GET data-api.polymarket.com/positions for any wallet address. py-clob-client-v2 exposes balance and allowance via get_balance_allowance(), but position tracking is a Data API job. See the py_clob_client Reference for the client’s balance/allowance methods.

What is MarketOrderArgs in py_clob_client?

MarketOrderArgs is the data class used to specify market orders (fill-or-kill). It takes token_id, amount (in USDC), side, and order_type. Use it with client.create_market_order(). See the MarketOrderArgs reference for the full field reference and examples.

Where This Fits in the Agent Betting Stack

This guide covers Layer 3 (Trading) of the Agent Betting Stack. Polymarket’s API is the execution layer — where your agent converts intelligence into positions.

To build a complete autonomous agent, you also need:

• Layer 1 — Identity: Register and verify your agent (Moltbook Identity Guide)
• Layer 2 — Wallet: Hold and manage funds autonomously (Wallet Comparison Guide)
• Layer 4 — Intelligence: Agent Intelligence Guide — LLM analysis, sentiment, and strategy
• Arbitrage: Cross-Market Arbitrage Guide — Arb across Polymarket, Kalshi, and sportsbooks

This guide is maintained by AgentBets.ai. Found an error or API change we missed? Let us know on Twitter.

Not financial advice. Built for builders.