Home/Learn/MEV and Front-Running: Why Transaction Order Matters
Back to Learning Hub

MEV and Front-Running: Why Transaction Order Matters

A plain-English guide to miner or maximal extractable value, sandwich attacks, and transaction ordering risk.

Reviewed by Pavlo Nakonechnyi
Updated 2026-05-11

MEV stands for maximal extractable value. It refers to value that validators, block builders, or bots can capture by controlling or reacting to transaction order.

How Front-Running Happens

Pending transactions are often visible before confirmation. Bots can copy, reorder, or surround a trade to profit from expected price movement.

Why Users Notice It

The most common user-facing MEV issue is a sandwich attack, where a bot buys before your swap and sells after it, leaving you with a worse execution price.

Common MEV Patterns

MEV is not always malicious, but users usually feel it through worse execution.

Pattern What happens
Sandwich attack A bot buys before your trade and sells after it.
Back-running A bot trades immediately after a transaction that changes price.
Liquidation capture Searchers compete to liquidate risky borrowing positions.
Arbitrage Bots equalize prices across pools or exchanges.

Why Slippage Settings Matter

A high slippage tolerance gives sandwich bots more room to extract value. Thin pools and large trades are easier targets because a single swap moves the price more.

How TokenRadar Applies This

TokenRadar connects MEV risk to liquidity depth, volatility, and trade size. A token may look liquid by volume but still expose users to poor execution if the actual pool depth is weak.

Practical Defense

Use limit orders or protected routing when available, keep slippage tight for liquid assets, split large swaps carefully, and avoid trading new tokens during chaotic launch windows unless you understand the execution risk.