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Maximum Extractable Value (MEV) protection shields your transactions from front-running, sandwich attacks, and other forms of MEV extraction by routing them through OKX’s private transaction infrastructure.

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What is MEV?

MEV (Maximum Extractable Value) refers to the profit that can be extracted by reordering, inserting, or censoring transactions within a block. Common MEV attacks include:

Front-running

An attacker sees your pending transaction and submits a similar one with higher gas to execute first

Sandwich attacks

An attacker places transactions before and after yours to profit from the price impact

Back-running

An attacker executes a transaction immediately after yours to capitalize on price changes

Transaction reordering

Miners or validators reorder transactions to maximize their profit

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How MEV protection works

When you enable MEV protection, your transaction is:
  1. Sent to OKX’s private mempool instead of the public mempool
  2. Hidden from public searchers and MEV bots
  3. Included directly in blocks by trusted validators
  4. Protected from front-running and sandwich attacks
MEV protection requires API registration and whitelist approval. Contact [email protected] to request access.

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Enabling MEV protection

To enable MEV protection, set enableMevProtection: true when broadcasting your transaction: 
const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTransaction,
  chainIndex: '8453',
  address: walletAddress,
  enableMevProtection: true  // Enable MEV protection
});

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Complete example

Here’s a complete swap workflow with MEV protection from the SDK source code: 
import { OKXDexClient } from '@okx-dex/okx-dex-sdk';
import { ethers } from 'ethers';
import { createEVMWallet } from '@okx-dex/okx-dex-sdk/core/evm-wallet';

const provider = new ethers.JsonRpcProvider(process.env.EVM_RPC_URL!);
const wallet = createEVMWallet(process.env.EVM_PRIVATE_KEY!, provider);

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!,
  evm: { wallet }
});

const walletAddress = wallet.address;

// Step 1: Get swap data
const swapData = await client.dex.getSwapData({
  chainIndex: '8453',
  fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
  amount: '3000000000000000',
  slippagePercent: '0.05',
  userWalletAddress: walletAddress
});

const txData = swapData.data[0].tx;

// Step 2: Sign the transaction
const nonce = await provider.getTransactionCount(walletAddress);

const transaction = {
  to: txData.to,
  value: txData.value,
  data: txData.data,
  gasLimit: txData.gas,
  gasPrice: txData.gasPrice,
  nonce: nonce,
  chainId: 8453
};

const signedTx = await wallet.signTransaction(transaction);

// Step 3: Broadcast with MEV protection
const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: signedTx,
  chainIndex: '8453',
  address: walletAddress,
  enableMevProtection: true  // Protected from MEV attacks
});

console.log('Order ID:', broadcastResult.data[0].orderId);
console.log('Transaction Hash:', broadcastResult.data[0].txHash);

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When to use MEV protection

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Solana: Jito MEV protection

For Solana transactions, you can use Jito’s MEV protection by providing a Jito-signed transaction: 
const broadcastResult = await client.dex.broadcastTransaction({
  signedTx: regularSignedTx,
  chainIndex: '501',  // Solana
  address: walletAddress,
  jitoSignedTx: jitoSignedTransaction  // Jito bundle
});
Jito bundles provide MEV protection on Solana by guaranteeing transaction ordering within a bundle.

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Monitoring protected transactions

Track your MEV-protected transactions using the order ID: 
const orders = await client.dex.getTransactionOrders({
  orderId: broadcastResult.data[0].orderId,
  chainIndex: '8453',
  address: walletAddress
});

console.log('Status:', orders.data[0].orders[0].txStatus);
console.log('Transaction Hash:', orders.data[0].orders[0].txHash);
See the Order tracking guide for more details.

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Cost considerations

MEV protection may involve additional fees depending on your API tier. Check with OKX for current pricing.
While MEV protection may have a small cost, it often saves money by preventing:
  • Front-running losses
  • Sandwich attack slippage
  • Failed transactions due to MEV
  • Unfavorable price execution

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Best practices

Always use MEV protection in production applications to protect your users from MEV attacks.
const isProduction = process.env.NODE_ENV === 'production';
const enableMevProtection = isProduction;  // Always true in production

await client.dex.broadcastTransaction({
  signedTx,
  chainIndex: '8453',
  address: walletAddress,
  enableMevProtection
});
Use MEV protection together with appropriate slippage settings for maximum protection.
const swapData = await client.dex.getSwapData({
  chainIndex: '8453',
  fromTokenAddress,
  toTokenAddress,
  amount,
  slippagePercent: '0.005',  // 0.5% slippage
  userWalletAddress
});

const signedTx = await wallet.signTransaction(transaction);

await client.dex.broadcastTransaction({
  signedTx,
  chainIndex: '8453',
  address: walletAddress,
  enableMevProtection: true  // MEV + slippage protection
});
Track your protected transactions to ensure they’re confirmed.
const broadcastResult = await client.dex.broadcastTransaction({
  signedTx,
  chainIndex: '8453',
  address: walletAddress,
  enableMevProtection: true
});

const orderId = broadcastResult.data[0].orderId;

// Poll for status
const pollStatus = async () => {
  const orders = await client.dex.getTransactionOrders({
    orderId,
    chainIndex: '8453',
    address: walletAddress
  });
  
  const status = orders.data[0].orders[0].txStatus;
  
  if (status === '2') {
    console.log('✅ Transaction confirmed!');
  } else if (status === '3') {
    console.error('❌ Transaction failed');
  } else {
    setTimeout(pollStatus, 3000);  // Poll every 3 seconds
  }
};

pollStatus();

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Comparison: With vs without MEV protection

AspectWithout ProtectionWith MEV Protection
VisibilityPublic mempoolPrivate mempool
Front-running riskHighNone
Sandwich attacksPossiblePrevented
Price executionMay be unfavorableGuaranteed
Confirmation timeVariableTypically faster
CostGas onlyGas + potential MEV fee

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Next steps

Transaction broadcasting

Learn about the complete broadcasting workflow

Order tracking

Monitor your transaction status

Slippage protection

Configure slippage tolerance

API reference

View the complete API reference

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