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The CLOB uses two levels of authentication: L1 (Private Key) and L2 (API Key). Either can be accomplished using the CLOB client or REST API. Authentication is not required to access client public methods and public endpoints.

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Authentication Levels

L1 Authentication

Use the private key of the user’s account to sign messages

L2 Authentication

Use API credentials (key, secret, passphrase) to authenticate requests to the CLOB

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L1 Authentication

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What is L1?

L1 authentication uses the wallet’s private key to sign an EIP-712 message used in the request header. It proves ownership and control over the private key. The private key stays in control of the user and all trading activity remains non-custodial.

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What This Enables

Access to L1 methods that create or derive L2 authentication headers.
  • Create user API credentials
  • Derive existing user API credentials
  • Sign/create user’s orders locally

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CLOB Client

  • TypeScript
  • Python
import { ClobClient } from "@polymarket/clob-client";
import { Wallet } from "ethers"; // v5.8.0

const HOST = "https://clob.polymarket.com";
const CHAIN_ID = 137; // Polygon mainnet
const signer = new Wallet(process.env.PRIVATE_KEY);

const client = new ClobClient(
  HOST,
  CHAIN_ID,
  signer // Signer enables L1 methods
);

// Gets API key, or else creates
const apiCreds = await client.createOrDeriveApiKey();

/*
apiCreds = {
  "apiKey": "550e8400-e29b-41d4-a716-446655440000",
  "secret": "base64EncodedSecretString",
  "passphrase": "randomPassphraseString"
}
*/
Never commit private keys to version control. Always use environment variables or secure key management systems.

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REST API

While we highly recommend using our provided clients to handle signing and authentication, the following is for developers who choose NOT to use our Python or TypeScript clients. When making direct REST API calls with L1 authentication, include these headers:
HeaderRequired?Description
POLY_ADDRESSyesPolygon signer address
POLY_SIGNATUREyesCLOB EIP 712 signature
POLY_TIMESTAMPyesCurrent UNIX timestamp
POLY_NONCEyesNonce. Default 0
The POLY_SIGNATURE is generated by signing the following EIP-712 struct. 
const domain = {
  name: "ClobAuthDomain",
  version: "1",
  chainId: chainId, // Polygon Chain ID 137
};

const types = {
  ClobAuth: [
    { name: "address", type: "address" },
    { name: "timestamp", type: "string" },
    { name: "nonce", type: "uint256" },
    { name: "message", type: "string" },
  ],
};

const value = {
  address: signingAddress, // The Signing address
  timestamp: ts,            // The CLOB API server timestamp
  nonce: nonce,             // The nonce used
  message: "This message attests that I control the given wallet",
};

const sig = await signer._signTypedData(domain, types, value);
Reference implementations:
Create API Credentials Create new API credentials for user. 
POST {clob-endpoint}/auth/api-key
Derive API Credentials Derive API credentials for user. 
GET {clob-endpoint}/auth/derive-api-key
Response 
{
  "apiKey": "550e8400-e29b-41d4-a716-446655440000",
  "secret": "base64EncodedSecretString",
  "passphrase": "randomPassphraseString"
}
You’ll need all three values for L2 authentication.

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L2 Authentication

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What is L2?

The next level of authentication is called L2, and it consists of the user’s API credentials (apiKey, secret, passphrase) generated from L1 authentication. These are used solely to authenticate requests made to the CLOB API. Requests are signed using HMAC-SHA256.

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What This Enables

Access to L2 methods such as posting signed/created orders, viewing open orders, cancelling open orders, getting trades
  • Cancel or get user’s open orders
  • Check user’s balances and allowances
  • Post user’s signed orders

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CLOB Client

  • TypeScript
  • Python
import { ClobClient } from "@polymarket/clob-client";
import { Wallet } from "ethers"; // v5.8.0

const HOST = "https://clob.polymarket.com";
const CHAIN_ID = 137; // Polygon mainnet
const signer = new Wallet(process.env.PRIVATE_KEY);

const client = new ClobClient(
  HOST,
  CHAIN_ID,
  signer,
  apiCreds, // Generated from L1 auth, API credentials enable L2 methods
  1, // signatureType explained below
  FUNDER // funder explained below
);

// Now you can trade!*
const order = await client.createAndPostOrder(
  { tokenID: "123456", price: 0.65, size: 100, side: "BUY" },
  { tickSize: "0.01", negRisk: false }
);
Even with L2 authentication headers, methods that create user orders still require the user to sign the order payload.

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REST API

While we highly recommend using our provided clients to handle signing and authentication, the following is for developers who choose NOT to use our Python or TypeScript clients. When making direct REST API calls with L2 authentication, include these headers:
HeaderRequired?Description
POLY_ADDRESSyesPolygon signer address
POLY_SIGNATUREyesHMAC signature for request
POLY_TIMESTAMPyesCurrent UNIX timestamp
POLY_API_KEYyesUser’s API apiKey value
POLY_PASSPHRASEyesUser’s API passphrase value
The POLY_SIGNATURE for L2 is an HMAC-SHA256 signature created using the user’s API credentials secret value. Reference implementations can be found in the Typescript and Python clients.

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Signature Types and Funder

When initializing the L2 client, you must specify your wallet signatureType and the funder address which holds the funds:
Signature TypeValueDescription
EOA0Standard Ethereum wallet (MetaMask). Funder is the EOA address and will need POL to pay gas on transactions.
POLY_PROXY1A custom proxy wallet only used with users who logged in via Magic Link email/Google. Using this requires the user to have exported their PK from Polymarket.com and imported into your app.
GNOSIS_SAFE2Gnosis Safe multisig proxy wallet (most common). Use this for any new or returning user who does not fit the other 2 types.
The wallet addresses displayed to the user on Polymarket.com is the proxy wallet and should be used as the funder. These can be deterministically derived or you can deploy them on behalf of the user. These proxy wallets are automatically deployed for the user on their first login to Polymarket.com.

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Troubleshooting

Your wallet’s private key is incorrect or improperly formatted.Solution:
  • Verify your private key is a valid hex string (starts with “0x”)
  • Ensure you’re using the correct key for the intended address
  • Check that the key has proper permissions
The nonce you provided has already been used to create an API key.Solution:
  • Use deriveApiKey() with the same nonce to retrieve existing credentials
  • Or use a different nonce with createApiKey()
Your funder address is incorrect or doesn’t match your wallet.Solution: Check your Polymarket profile address at polymarket.com/settings.If it does not exist or user has never logged into Polymarket.com, deploy it first before creating L2 authentication.
// Use deriveApiKey with the original nonce
const recovered = await client.deriveApiKey(originalNonce);
Unfortunately, there’s no way to recover lost API credentials without the nonce. You’ll need to create new credentials:
// Create fresh credentials with a new nonce
const newCreds = await client.createApiKey();
// Save the nonce this time!

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See Client Methods

Public Methods

Access market data, orderbooks, and prices.

L1 Methods

Private key authentication to create or derive API keys (L2 headers).

L2 Methods

Manage and close orders. Creating orders requires signer.

Builder Program Methods

Builder-specific operations for those in the Builders Program.