How Does Front-Running Differ From a Sandwich Attack?

Both exploit the same underlying visibility — a bot seeing your pending transaction before it confirms — but they use that visibility differently, target different situations, and leave you affected in distinct ways.

The Core Structural Difference

Front-running is a single action: a bot copies or acts on a profitable opportunity it sees pending, executing before the original transaction does. A sandwich attack is two actions surrounding one target: a transaction placed before yours, and another placed after — your trade is sandwiched between them.

What Each Technique Is Actually Targeting

Pure front-running targets an opportunity itself — a profitable trade, an arbitrage window, a liquidation about to become available — racing to capture it before the original transaction that revealed it can complete. A sandwich attack specifically targets your transaction's execution price, engineering a worse outcome for you rather than simply beating you to something separate.

Why Front-Running Doesn't Necessarily Require Your Trade to Move the Price

A bot front-running a profitable opportunity is often just racing to capture something first — it doesn't need your specific transaction to move the market at all, only to reveal that the opportunity exists. A sandwich attack, by contrast, specifically relies on your transaction's own price impact to generate its profit on the exit side.

Why a Sandwich Attack Requires Two Coordinated Transactions

Front-running can succeed with a single, well-timed transaction. A sandwich attack requires the bot to execute both a buy before your transaction and a sell after it, with your transaction landing precisely in between — a more coordinated, structurally dependent sequence than simple front-running.

Why the Financial Impact on You Differs

If a bot front-runs an opportunity unrelated to your specific trade, your own transaction may execute at exactly the price you expected, unaffected. A sandwich attack directly and specifically worsens the price your transaction receives — the harm is inherent to the structure, not incidental.

Why Both Are Grouped Under the Same Broader Category

Front-running and sandwich attacks are both forms of MEV — value extracted through control over transaction visibility and ordering — which is why they're often discussed together, even though the specific mechanics and targets differ.

Why the Same Protections Generally Apply to Both

Since both depend on mempool visibility, a private transaction relay addresses both equally by removing that visibility at the source. Slippage tolerance specifically limits sandwich attack damage more directly, since front-running doesn't necessarily worsen your own transaction's execution price the same way.

Check a pool's liquidity before trading a meaningful amount — both front-running and sandwich attacks become more profitable for bots on thinner, more easily moved pools.