How to tell if your Ethereum swap was sandwiched

If a swap gave you noticeably fewer tokens than the quote, a sandwich attack is the usual suspect. You can check it yourself on Etherscan.

Step 1. Open your transaction

In your wallet's activity list, open the swap and choose "View on block explorer", or paste the transaction hash into etherscan.io. Note the block number and the token you bought or sold.

Step 2. Look at the transactions right around yours

Click the block number to open the block, and find your transaction in the list. A sandwich puts one transaction directly before yours and one directly after, in the same block.

Step 3. Compare the one before and the one after

It is a sandwich when all of these are true:

• The transaction before yours buys the same token you bought (or sells the one you sold), in the same pool.
• The transaction after yours does the opposite trade in the same pool.
• Both come from the same address or the same contract.
• You received less than the quote, close to your minimum after slippage.

Open each transaction and check the "Token Transfers" section to see which tokens moved and through which pool.

A shortcut

MEV explorers such as EigenPhi label sandwich attacks automatically. Searching your transaction hash there will usually show whether it was sandwiched and how much the bot made.

What to do next

A sandwich only works because the bot saw your swap in the public mempool before it was included. Tighter slippage limits the damage; a private RPC prevents it. See how to avoid sandwich attacks on Ethereum.