Gasless Token Swaps

Swap tokens without users needing ETH or native tokens for gas. Biconomy handles gas abstraction—users can pay fees in the token they’re swapping, or you can sponsor gas entirely.

How It Works

User Initiates Swap

User selects tokens and amount to swap

API Finds Best Route

Biconomy finds optimal route across DEXs and bridges

User Signs Once

Single signature approves the entire swap—no separate gas transaction

MEE Executes

Biconomy relayers execute and pay gas, deducting fee from swap or your sponsorship

Quick Example

Swap 100 USDC on Base to USDT on Optimism—completely gasless:

// 1. Request a quote
const quote = await fetch('https://api.biconomy.io/v1/quote', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    mode: 'smart-account',
    ownerAddress: '0xYourAddress',
    // No feeToken = sponsored (gasless)
    composeFlows: [{
      type: '/instructions/intent-simple',
      data: {
        srcChainId: 8453,           // Base
        dstChainId: 10,             // Optimism
        srcToken: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913',  // USDC
        dstToken: '0x94b008aa00579c1307b0ef2c499ad98a8ce58e58',  // USDT
        amount: '100000000',        // 100 USDC (6 decimals)
        slippage: 0.01              // 1%
      }
    }]
  })
}).then(r => r.json());

// 2. Sign the payload
const signature = await wallet.signMessage({
  message: quote.payloadToSign[0].signablePayload.message
});

// 3. Execute
const result = await fetch('https://api.biconomy.io/v1/execute', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    ...quote,
    payloadToSign: [{ ...quote.payloadToSign[0], signature }]
  })
}).then(r => r.json());

console.log('Track at:', `https://meescan.biconomy.io/details/${result.supertxHash}`);

Two Ways to Go Gasless

Sponsored (You Pay)
User Pays in Token

Best for: Onboarding flows, premium users, promotional campaignsOmit the feeToken parameter—gas is paid from your sponsorship account:

{
  mode: 'smart-account',
  ownerAddress: userAddress,
  // No feeToken = use sponsorship
  composeFlows: [...]
}

Requires an API key with sponsorship enabled. Get one at dashboard.biconomy.io

Best for: Regular transactions where users cover costsSet feeToken to deduct gas from the token being swapped:

{
  mode: 'smart-account',
  ownerAddress: userAddress,
  feeToken: {
    address: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913', // USDC
    chainId: 8453
  },
  composeFlows: [...]
}

User still signs once—fee is automatically deducted from their USDC.

Works with Any Wallet

Smart Accounts

Use mode: 'smart-account' for Nexus or ERC-4337 accounts. Native gas abstraction.

EOA Wallets

Use mode: 'eoa' for MetaMask, Rabby, etc. Requires fundingTokens parameter.

EOA Example (MetaMask, Rabby, etc.)

const quote = await fetch('https://api.biconomy.io/v1/quote', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    mode: 'eoa',
    ownerAddress: userAddress,
    fundingTokens: [{
      tokenAddress: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913',
      chainId: 8453,
      amount: '100000000'
    }],
    feeToken: {
      address: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913',
      chainId: 8453
    },
    composeFlows: [{
      type: '/instructions/intent-simple',
      data: {
        srcChainId: 8453,
        dstChainId: 10,
        srcToken: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913',
        dstToken: '0x94b008aa00579c1307b0ef2c499ad98a8ce58e58',
        amount: '100000000',
        slippage: 0.01
      }
    }]
  })
}).then(r => r.json());

Understanding the Response

The quote response tells you exactly what will happen:

{
  "fee": {
    "amount": "50000",           // Fee in token units
    "token": "0x833589...",      // Fee token address
    "chainId": 8453
  },
  "returnedData": [{
    "outputAmount": "99500000",  // Expected output
    "minOutputAmount": "98505000", // After slippage
    "route": {
      "summary": "lifi[uniswap] => across",
      "estimatedTime": 120
    }
  }]
}

Field	What It Means
`fee.amount`	How much gas costs (in fee token units)
`outputAmount`	Expected tokens user will receive
`minOutputAmount`	Minimum after slippage protection
`route.summary`	Which DEXs/bridges will be used

Getting Started

Tutorials

How It Works

Quick Example

Two Ways to Go Gasless

Works with Any Wallet

Smart Accounts

EOA Wallets

EOA Example (MetaMask, Rabby, etc.)

Understanding the Response

Next Steps

Cross-Chain Swaps

Full API Tutorial

​How It Works

​Quick Example

​Two Ways to Go Gasless

​Works with Any Wallet

Smart Accounts

EOA Wallets

​EOA Example (MetaMask, Rabby, etc.)

​Understanding the Response

​Next Steps

Cross-Chain Swaps

Full API Tutorial

How It Works

Quick Example

Two Ways to Go Gasless

Works with Any Wallet

EOA Example (MetaMask, Rabby, etc.)

Understanding the Response

Next Steps