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Native Token Swaps

The CoW Protocol SDK enables selling blockchain native tokens (ETH, MATIC, etc.) through the EthFlow contract. Since native tokens aren’t ERC-20 compliant, they require special handling for on-chain transactions.

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How It Works

When selling native tokens:
  1. An on-chain transaction is sent to the EthFlow contract
  2. Native tokens are locked in the contract
  3. An order is created in the CoW Protocol order book
  4. Upon filling, the buyer receives their tokens
  5. Unfilled orders can be cancelled to reclaim funds
Only selling native tokens is supported. To buy native tokens, trade for wrapped versions (e.g., WETH) first.

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Using postSwapOrder (Automatic Detection)

The SDK automatically detects native token orders using the special marker address 0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE and routes them through EthFlow. 
import {
  SupportedChainId,
  OrderKind,
  TradeParameters,
  TradingSdk
} from '@cowprotocol/sdk-trading'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { createPublicClient, http, privateKeyToAccount } from 'viem'
import { sepolia } from 'viem/chains'

const adapter = new ViemAdapter({
  provider: createPublicClient({
    chain: sepolia,
    transport: http('YOUR_RPC_URL')
  }),
  signer: privateKeyToAccount('YOUR_PRIVATE_KEY' as `0x${string}`)
})

const sdk = new TradingSdk({
  chainId: SupportedChainId.SEPOLIA,
  appCode: 'YOUR_APP_CODE',
}, {}, adapter)

const parameters: TradeParameters = {
  kind: OrderKind.SELL,
  sellToken: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  sellTokenDecimals: 18,
  buyToken: '0x0625afb445c3b6b7b929342a04a22599fd5dbb59',
  buyTokenDecimals: 18,
  amount: '100000000000000000', // 0.1 ETH
}

const { orderId, txHash } = await sdk.postSwapOrder(parameters)

console.log('Order ID:', orderId)
console.log('Transaction hash:', txHash)

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Using postSellNativeCurrencyOrder

For more control, use the dedicated postSellNativeCurrencyOrder method:

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Method Signature

postSellNativeCurrencyOrder(
  params: TradeParameters,
  advancedSettings?: SwapAdvancedSettings
): Promise<{
  orderId: string
  txHash: string
  signingScheme: SigningScheme
  signature: string
  orderToSign: UnsignedOrder
}>

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Example

import {
  SupportedChainId,
  OrderKind,
  TradeParameters,
  TradingSdk
} from '@cowprotocol/sdk-trading'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { createPublicClient, http, privateKeyToAccount } from 'viem'
import { sepolia } from 'viem/chains'

const adapter = new ViemAdapter({
  provider: createPublicClient({
    chain: sepolia,
    transport: http('YOUR_RPC_URL')
  }),
  signer: privateKeyToAccount('YOUR_PRIVATE_KEY' as `0x${string}`)
})

const sdk = new TradingSdk({
  chainId: SupportedChainId.SEPOLIA,
  appCode: 'YOUR_APP_CODE',
}, {}, adapter)

const parameters: TradeParameters = {
  kind: OrderKind.SELL,
  sellToken: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  sellTokenDecimals: 18,
  buyToken: '0x0625afb445c3b6b7b929342a04a22599fd5dbb59',
  buyTokenDecimals: 18,
  amount: '100000000000000000', // 0.1 ETH
}

const result = await sdk.postSellNativeCurrencyOrder(parameters)

console.log('Order created:', result.orderId)
console.log('Transaction:', result.txHash)

// Wait for transaction confirmation
await adapter.provider.waitForTransactionReceipt({ hash: result.txHash })
console.log('Transaction confirmed!')

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Complete Example with Quote

import {
  TradingSdk,
  SupportedChainId,
  OrderKind,
  TradeParameters,
} from '@cowprotocol/sdk-trading'
import { parseEther } from 'viem'

const sdk = new TradingSdk({
  chainId: SupportedChainId.MAINNET,
  appCode: 'YOUR_APP_CODE',
}, {}, adapter)

const parameters: TradeParameters = {
  kind: OrderKind.SELL,
  sellToken: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  sellTokenDecimals: 18,
  buyToken: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48', // USDC
  buyTokenDecimals: 6,
  amount: parseEther('1').toString(), // 1 ETH
}

// Step 1: Get a quote
const { quoteResults } = await sdk.getQuote(parameters)

const expectedUSDC = quoteResults.amountsAndCosts.afterSlippage.buyAmount
const ethAmount = parseEther('1')

console.log(`Selling ${ethAmount} ETH`)
console.log(`Expected to receive at least: ${expectedUSDC} USDC`)

// Step 2: Create the order
if (confirm('Proceed with the trade?')) {
  const { orderId, txHash } = await sdk.postSellNativeCurrencyOrder(parameters)

  console.log('Order ID:', orderId)
  console.log('Transaction hash:', txHash)

  await adapter.provider.waitForTransactionReceipt({ hash: txHash })
  console.log('Order created successfully!')
}

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Order Kinds for Native Tokens

const parameters: TradeParameters = {
  kind: OrderKind.SELL,
  sellToken: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  sellTokenDecimals: 18,
  buyToken: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48',
  buyTokenDecimals: 6,
  amount: '1000000000000000000', // 1 ETH
}

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Gas Cost Considerations

Native token orders require on-chain transactions, making them significantly more expensive than regular orders:
OperationGas UsageEstimated Cost
EthFlow order creation~150,000-200,000~15−15-20
Regular orders0 gasFree (off-chain)
Cancellation~50,000-70,000 gas~5−5-7
Always ensure you have enough ETH for gas in addition to the amount you’re selling.

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Cancelling Native Token Orders

import { TradingSdk } from '@cowprotocol/sdk-trading'

const sdk = new TradingSdk({
  chainId: SupportedChainId.MAINNET,
  appCode: 'YOUR_APP_CODE',
}, {}, adapter)

const { orderId, txHash } = await sdk.postSellNativeCurrencyOrder(parameters)

// Try off-chain cancellation first
try {
  await sdk.offChainCancelOrder({ orderUid: orderId })
  console.log('Order cancelled (soft)')
} catch (error) {
  // Fall back to on-chain cancellation (refunds locked ETH)
  const cancelTxHash = await sdk.onChainCancelOrder({ orderUid: orderId })
  console.log('Cancellation transaction:', cancelTxHash)

  await adapter.provider.waitForTransactionReceipt({ hash: cancelTxHash })
  console.log('Order cancelled and ETH refunded')
}

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Advanced: Custom EthFlow Parameters

import { SwapAdvancedSettings, SigningScheme } from '@cowprotocol/sdk-trading'

const advancedSettings: SwapAdvancedSettings = {
  quoteRequest: {
    signingScheme: SigningScheme.EIP1271,
    onchainOrder: true,
    verificationGasLimit: 0,
    validFor: 3600, // 1 hour
  },
}

const { orderId, txHash } = await sdk.postSellNativeCurrencyOrder(
  parameters,
  advancedSettings
)

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Common Chains and Native Tokens

ChainNative TokenAddress to Use
EthereumETH0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE
GnosisxDAI0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE
ArbitrumETH0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE
SepoliaETH0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE

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Best Practices

  1. Verify sufficient balance for both the order amount and gas fees
  2. Use OrderKind.SELL for better predictability with native tokens
  3. Wait for transaction confirmation before querying order status
  4. Consider wrapping to WETH for smaller amounts where gas costs might exceed savings
  5. Monitor gas prices before executing native token orders

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Next Steps

Last modified on March 4, 2026