How to cancel a pending Ethereum transaction
Cancelling a pending Ethereum transaction does not 'delete' it — it overwrites it. You send a new transaction with the same nonce that transfers 0 ETH to your own address, paying a higher fee. When it is mined, the original transfer is replaced by a harmless no-op.
Why it works. Two transactions from the same address cannot share a nonce. The network keeps only the replacement that pays a sufficient fee, so the original pending transfer is dropped.
The steps. Note the pending transaction's nonce, then broadcast a 0-ETH transfer to yourself with that same nonce and a fee at least 10% higher. Most wallets expose this as a 'Cancel' button.
The cost. Cancelling is not free. The replacement is a real on-chain transaction and pays its own gas — roughly the cost of a basic ETH transfer.
Quick answers
Is cancelling a transaction free?
No. The replacement is a real transaction that pays gas, about the same as a standard ETH transfer. You pay for the cancellation, not for the original transfer.
What if I cancel and the original was already mined?
If the original confirms first, the cancellation has nothing to replace and does nothing. Check the original's status before cancelling.
Can I cancel a token (ERC-20) transfer?
Yes, the same way — a zero-value same-nonce replacement overwrites the pending token transfer. The token transfer simply does not go through.