ethereum/mev-protection

MEV Protection and Flashbots Guide

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v1.0.0·Updated 3/20/2026

MEV Types Quick Reference

Type	Mechanism	Victim	Scale
Sandwich Attack	Insert transactions before and after target swap to capture price difference	DEX users	Most common
Frontrunning	Copy target transaction with higher gas to execute first	NFT minters, arbitrageurs
Backrunning	Execute after target transaction to capture price impact	No direct victim (arbitrage)
Liquidation MEV	Race to trigger liquidations for rewards	Liquidated users

User-Side Protection

1. Use Private RPC (Simplest)

# Flashbots Protect RPC (Mainnet, free)
https://rpc.flashbots.net

# MEV Blocker (aggregated protection)
https://rpc.mevblocker.io

# Metamask setup: Settings → Networks → Ethereum Mainnet → Replace RPC URL

Private RPCs send transactions directly to validators, bypassing the public mempool so bots cannot monitor them.

2. Set Reasonable Slippage

- Mainstream tokens (ETH/USDC): 0.1% - 0.5%
- Medium liquidity: 0.5% - 1%
- Don't exceed 1% (unless liquidity is extremely poor)
- Don't use "auto" (Uniswap defaults to 0.5%, but increases during market volatility)

Contract-Side Protection

1. Commit-Reveal (Prevent NFT Mint Frontrunning)

// Phase 1: Submit hash (without revealing content)
mapping(address => bytes32) public commits;
function commit(bytes32 hash) external {
  commits[msg.sender] = hash;
}

// Phase 2: Reveal (verify hash matches)
function reveal(uint256 choice, bytes32 salt) external {
  require(commits[msg.sender] == keccak256(abi.encode(choice, salt, msg.sender)));
  // Execute operation
}

2. Minimize Slippage Window (AMM Integration)

// ❌ Unprotected: allows arbitrary price slippage
router.exactInputSingle({..., amountOutMinimum: 0});

// ✅ On-chain TWAP verification (prevent large deviations)
uint256 twapPrice = getTWAP(pool, 30 minutes);
uint256 minOut = twapPrice * amountIn * 99 / 100;  // Allow 1% deviation
router.exactInputSingle({..., amountOutMinimum: minOut});

3. Use Flashbots Bundles (Contract Interaction)

import { FlashbotsBundleProvider } from "@flashbots/ethers-provider-bundle"

const flashbotsProvider = await FlashbotsBundleProvider.create(
  provider,
  authSigner,  // Random signer for authentication
  'https://relay.flashbots.net'
)

const bundle = [
  { transaction: tx1, signer: wallet },
  { transaction: tx2, signer: wallet },
]

const targetBlock = await provider.getBlockNumber() + 1
const response = await flashbotsProvider.sendBundle(bundle, targetBlock)

Bundle characteristics:

Atomicity: all succeed or all fail
Does not enter public mempool
Gas only paid on success

4. Price Protection (Protocol Layer)

// Limit single transaction impact
uint256 constant MAX_PRICE_IMPACT = 500; // 5%

function swap(uint amountIn) external {
  uint priceBefore = getPrice();
  _executeSwap(amountIn);
  uint priceAfter = getPrice();
  
  uint impact = (priceBefore - priceAfter) * 10000 / priceBefore;
  require(impact <= MAX_PRICE_IMPACT, "Price impact too high");
}

MEV Monitoring Tools

EigenPhi (eigenphi.io) — MEV visualization and analysis
Flashbots Explorer (explorer.flashbots.net) — Bundle history
mev-inspect-py — Self-hosted MEV analysis
libmev — Real-time MEV data API