Gasless Transactions

Polymarket’s Relayer Client enables gasless transactions for your users. Instead of requiring users to hold POL for gas, Polymarket’s infrastructure pays all transaction fees. This creates a seamless experience where users only need USDC.e to trade.

How It Works

The relayer acts as a transaction sponsor:

Your app creates a transaction
The user signs it with their private key
Your app sends it to Polymarket’s relayer
The relayer submits it onchain and pays the gas fee
The transaction executes from the user’s wallet

Gasless transactions require authentication with Builder API Keys or Relayer API Keys.

What Is Covered

Polymarket pays gas for all operations routed through the relayer:

Operation	Description
Wallet deployment	Deploy Safe or Proxy wallets for new users
Token approvals	Approve contracts to spend USDC.e or outcome tokens
CTF operations	Split, merge, and redeem positions
Transfers	Move tokens between addresses

Authentication

The relayer supports two authentication methods. Choose the one that fits your use case.

Using Builder API Keys

Builder API Keys are for Builder Program members. They authenticate via HMAC-SHA256 signed headers and are required to use the relayer SDKs. All requests must include these headers:

Header	Description
`POLY_BUILDER_API_KEY`	Your Builder API key
`POLY_BUILDER_TIMESTAMP`	Unix timestamp
`POLY_BUILDER_PASSPHRASE`	Your Builder passphrase
`POLY_BUILDER_SIGNATURE`	HMAC-SHA256 signature

The SDKs handle header generation automatically when you provide your credentials via BuilderConfig.

Using Relayer API Keys

Relayer API Keys are for market makers and anyone who needs a simpler alternative. You can create them from Settings > API Keys on the Polymarket website. Include these headers with your requests:

Header	Description
`RELAYER_API_KEY`	Your Relayer API key
`RELAYER_API_KEY_ADDRESS`	The address that owns the key

If you want to use the Relayer API Key directly without the SDK, see the Relayer API Reference.

Prerequisites

Before using the relayer, you need:

Requirement	Source
Builder API credentials or Relayer API key	Builder Profile or Settings > API Keys
User’s private key or signer	Your wallet integration
USDC.e balance	For trading (not for gas)

The below section is for the Builder SDKs only. If you want to use the Relayer API Key directly without the SDK, see the Relayer API Reference.

Installation

npm install @polymarket/builder-relayer-client @polymarket/builder-signing-sdk

Client Setup

Initialize the relayer client with your signing configuration:

Local Signing
Remote Signing

Use local signing when your backend handles all transactions securely.

import { createWalletClient, http, Hex } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { polygon } from "viem/chains";
import { RelayClient } from "@polymarket/builder-relayer-client";
import { BuilderConfig } from "@polymarket/builder-signing-sdk";

const account = privateKeyToAccount(process.env.PRIVATE_KEY as Hex);
const wallet = createWalletClient({
  account,
  chain: polygon,
  transport: http(process.env.RPC_URL),
});

const builderConfig = new BuilderConfig({
  localBuilderCreds: {
    key: process.env.POLY_BUILDER_API_KEY!,
    secret: process.env.POLY_BUILDER_SECRET!,
    passphrase: process.env.POLY_BUILDER_PASSPHRASE!,
  },
});

const client = new RelayClient(
  "https://relayer-v2.polymarket.com/",
  137,
  wallet,
  builderConfig,
);

Use remote signing to keep credentials on a secure server you control.Your signing server receives request details and returns authentication headers:

import {
  buildHmacSignature,
  BuilderApiKeyCreds,
} from "@polymarket/builder-signing-sdk";

const BUILDER_CREDENTIALS: BuilderApiKeyCreds = {
  key: process.env.POLY_BUILDER_API_KEY!,
  secret: process.env.POLY_BUILDER_SECRET!,
  passphrase: process.env.POLY_BUILDER_PASSPHRASE!,
};

// POST /sign endpoint
export async function handleSignRequest(request) {
  const { method, path, body } = await request.json();
  const timestamp = Date.now().toString();

  const signature = buildHmacSignature(
    BUILDER_CREDENTIALS.secret,
    parseInt(timestamp),
    method,
    path,
    body,
  );

  return {
    POLY_BUILDER_SIGNATURE: signature,
    POLY_BUILDER_TIMESTAMP: timestamp,
    POLY_BUILDER_API_KEY: BUILDER_CREDENTIALS.key,
    POLY_BUILDER_PASSPHRASE: BUILDER_CREDENTIALS.passphrase,
  };
}

Your client points to your signing server:

import { RelayClient } from "@polymarket/builder-relayer-client";
import { BuilderConfig } from "@polymarket/builder-signing-sdk";

const builderConfig = new BuilderConfig({
  remoteBuilderConfig: {
    url: "https://your-server.com/sign",
  },
});

const client = new RelayClient(
  "https://relayer-v2.polymarket.com/",
  137,
  wallet,
  builderConfig,
);

Never expose Builder API credentials in client-side code. Use environment variables or a secrets manager.

Wallet Types

Choose a wallet type when initializing the client:

Type	Deployment	Best For
Safe	Call `deploy()` before first transaction	Most builder integrations
Proxy	Auto-deploys on first transaction	Magic Link users

import { RelayClient, RelayerTxType } from "@polymarket/builder-relayer-client";

const client = new RelayClient(
  "https://relayer-v2.polymarket.com/",
  137,
  wallet,
  builderConfig,
  RelayerTxType.SAFE,
);

// Deploy before first transaction
const response = await client.deploy();
const result = await response.wait();
console.log("Safe Address:", result?.proxyAddress);

Executing Transactions

Use the execute method to send transactions through the relayer:

interface Transaction {
  to: string; // Target contract address
  data: string; // Encoded function call
  value: string; // POL to send (usually "0")
}

const response = await client.execute(transactions, "Description");
const result = await response.wait();

Token Approval

Approve contracts to spend tokens:

import { encodeFunctionData, maxUint256 } from "viem";

const USDC = "0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174";
const CTF = "0x4D97DCd97eC945f40cF65F87097ACe5EA0476045";

const approveTx = {
  to: USDC,
  data: encodeFunctionData({
    abi: [
      {
        name: "approve",
        type: "function",
        inputs: [
          { name: "spender", type: "address" },
          { name: "amount", type: "uint256" },
        ],
        outputs: [{ type: "bool" }],
      },
    ],
    functionName: "approve",
    args: [CTF, maxUint256],
  }),
  value: "0",
};

const response = await client.execute([approveTx], "Approve USDC.e for CTF");
await response.wait();

Redeem Positions

Exchange winning tokens for USDC.e after market resolution:

import { encodeFunctionData } from "viem";

const redeemTx = {
  to: CTF_ADDRESS,
  data: encodeFunctionData({
    abi: [
      {
        name: "redeemPositions",
        type: "function",
        inputs: [
          { name: "collateralToken", type: "address" },
          { name: "parentCollectionId", type: "bytes32" },
          { name: "conditionId", type: "bytes32" },
          { name: "indexSets", type: "uint256[]" },
        ],
        outputs: [],
      },
    ],
    functionName: "redeemPositions",
    args: [collateralToken, parentCollectionId, conditionId, indexSets],
  }),
  value: "0",
};

const response = await client.execute([redeemTx], "Redeem positions");
await response.wait();

Batch Transactions

Execute multiple operations atomically in a single call:

const approveTx = {
  to: USDC,
  data: encodeFunctionData({
    abi: erc20Abi,
    functionName: "approve",
    args: [CTF, maxUint256],
  }),
  value: "0",
};

const transferTx = {
  to: USDC,
  data: encodeFunctionData({
    abi: erc20Abi,
    functionName: "transfer",
    args: [recipientAddress, parseUnits("50", 6)],
  }),
  value: "0",
};

// Both execute atomically
const response = await client.execute(
  [approveTx, transferTx],
  "Approve and transfer",
);
await response.wait();

Batching reduces latency and ensures all transactions succeed or fail together.

Transaction States

Track transaction progress through these states:

State	Terminal	Description
`STATE_NEW`	No	Transaction received by relayer
`STATE_EXECUTED`	No	Submitted onchain
`STATE_MINED`	No	Included in a block
`STATE_CONFIRMED`	Yes	Finalized successfully
`STATE_FAILED`	Yes	Failed permanently
`STATE_INVALID`	Yes	Rejected as invalid

Getting Started

Core Concepts

Market Data

Trading

Market Makers

Builder Program

Resources

How It Works

What Is Covered

Authentication

Using Builder API Keys

Using Relayer API Keys

Prerequisites

Installation

Client Setup

Wallet Types

Executing Transactions

Token Approval

Redeem Positions

Batch Transactions

Transaction States

Contract Addresses

Resources

Next Steps

Negative Risk Markets

Positions & Tokens

Getting Started

Core Concepts

Market Data

Trading

Market Makers

Builder Program

Resources

​How It Works

​What Is Covered

​Authentication

​Using Builder API Keys

​Using Relayer API Keys

​Prerequisites

​Installation

​Client Setup

​Wallet Types

​Executing Transactions

​Token Approval

​Redeem Positions

​Batch Transactions

​Transaction States

​Contract Addresses

​Resources

​Next Steps

Negative Risk Markets

Positions & Tokens

How It Works

What Is Covered

Authentication

Using Builder API Keys

Using Relayer API Keys

Prerequisites

Installation

Client Setup

Wallet Types

Executing Transactions

Token Approval

Redeem Positions

Batch Transactions

Transaction States

Contract Addresses

Resources

Next Steps