PolymarketDocumentation/docs/developers/CLOB/introduction.md

Documentation Index

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Overview

Trading on the Polymarket CLOB

Polymarket's CLOB (Central Limit Order Book) is a hybrid-decentralized trading system — offchain order matching with onchain settlement via the Exchange contract (audited by Chainsecurity). All trading is non-custodial. Orders are EIP-712 signed messages, and matched trades settle atomically on Polygon. The operator cannot set prices or execute unauthorized trades — users can always cancel orders onchain independently.

We recommend using the open-source SDK clients, which handle order signing, authentication, and submission:

npm install @polymarket/clob-client

pip install py-clob-client

cargo add polymarket-client-sdk

You can also use the REST API directly, but you'll need to manage [EIP-712 order signing](https://github.com/Polymarket/clob-client/blob/main/src/signing/eip712.ts) and [HMAC authentication headers](https://github.com/Polymarket/clob-client/blob/main/src/signing/hmac.ts) yourself. See [REST API Headers](#rest-api-headers) below.

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Authentication

The CLOB uses two levels of authentication:

Level	Method	Purpose
L1	EIP-712 signature (private key)	Create or derive API credentials
L2	HMAC-SHA256 (API credentials)	Place orders, cancel orders, query trades

You use your private key once to derive L2 credentials (API key, secret, passphrase), which authenticate all subsequent trading requests.

```typescript TypeScript theme={null} import { ClobClient } from "@polymarket/clob-client"; import { Wallet } from "ethers"; // v5.8.0

const signer = new Wallet(process.env.PRIVATE_KEY);

// Derive L2 API credentials const tempClient = new ClobClient("https://clob.polymarket.com", 137, signer); const apiCreds = await tempClient.createOrDeriveApiKey();

```python Python theme={null}
from py_clob_client.client import ClobClient
import os

private_key = os.getenv("PRIVATE_KEY")

# Derive L2 API credentials
temp_client = ClobClient("https://clob.polymarket.com", key=private_key, chain_id=137)
api_creds = temp_client.create_or_derive_api_creds()

use std::str::FromStr;
use polymarket_client_sdk::POLYGON;
use polymarket_client_sdk::auth::{LocalSigner, Signer};
use polymarket_client_sdk::clob::{Client, Config};

let private_key = std::env::var("POLYMARKET_PRIVATE_KEY")?;
let signer = LocalSigner::from_str(&private_key)?
    .with_chain_id(Some(POLYGON));

// Derive L2 API credentials and initialize client in one step
let client = Client::new("https://clob.polymarket.com", Config::default())?
    .authentication_builder(&signer)
    .authenticate()
    .await?;

---

Signature Types

When initializing the trading client, you must specify your wallet's signature type and funder address:

Wallet Type	ID	When to Use	Funder Address
EOA	0	Standalone wallet — you pay your own gas (POL for gas)	Your EOA wallet address
POLY_PROXY	1	Polymarket account via Magic Link (email/Google login). Requires exported private key from Polymarket.com	Your proxy wallet address
GNOSIS_SAFE	2	Polymarket account via browser wallet (MetaMask, Rabby) or embedded wallet (Privy, Turnkey). Most common type	Your proxy wallet address

If you have a Polymarket.com account, your funds are in a proxy wallet visible in the profile dropdown. Use type `1` or `2`. Type `0` is for standalone EOA wallets only.

Initialize the Trading Client

```typescript TypeScript theme={null} const client = new ClobClient( "https://clob.polymarket.com", 137, signer, apiCreds, 2, // GNOSIS_SAFE "0x...", // Your proxy wallet address ); ```

client = ClobClient(
    "https://clob.polymarket.com",
    key=private_key,
    chain_id=137,
    creds=api_creds,
    signature_type=2,  # GNOSIS_SAFE
    funder="0x..."  # Your proxy wallet address
)

use polymarket_client_sdk::clob::types::SignatureType;

let client = Client::new("https://clob.polymarket.com", Config::default())?
    .authentication_builder(&signer)
    .signature_type(SignatureType::GnosisSafe) // Funder auto-derived via CREATE2
    .authenticate()
    .await?;

---

REST API Headers

If you're using the REST API directly (without the SDK), you need to attach authentication headers to each request.

L1 Headers — for creating or deriving API credentials:

Header	Description
POLY_ADDRESS	Your wallet address
POLY_SIGNATURE	EIP-712 signature
POLY_TIMESTAMP	Unix timestamp
POLY_NONCE	Request nonce

L2 Headers — for all trading operations (orders, cancellations, queries):

Header	Description
POLY_ADDRESS	Your wallet address
POLY_SIGNATURE	HMAC-SHA256 signature of the request
POLY_TIMESTAMP	Unix timestamp
POLY_API_KEY	Your API key
POLY_PASSPHRASE	Your API passphrase

Even with L2 authentication, methods that create orders still require the user's private key for EIP-712 order payload signing. L2 credentials authenticate the request, but the order itself must be signed by the key.

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Client Methods

Market data, orderbooks, prices, and spreads — no auth required. Sign orders and derive API credentials with your private key. Place orders, cancel orders, query trades, and manage notifications. Track attributed trades and manage builder credentials.

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What Is in This Section

Place your first order end-to-end Reading the orderbook, prices, spreads, and midpoints Order types, tick sizes, creating, cancelling, and querying orders Fee structure, fee-enabled markets, and maker rebates Execute onchain operations without paying gas Split, merge, and redeem outcome tokens Deposit and withdraw funds across chains

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