The Ethereum network can have its moments of congestion, causing transactions to remain unconfirmed for long periods of time. If you don't change any settings, new transactions you send will do little to speed up confirmations, and will be placed at the end of your queue needing wait for all previous ones to confirm.
This tutorial will show you how to properly replace or cancel an unconfirmed transaction on the Ethereum and other EVM networks, allowing it to confirm faster. You can replace base coin transactions, as well as tokens or DeFi operations.
- In Koala Wallet, open the details of the unconfirmed transaction
- Note the transaction's "Nonce" value
- Start a new transaction on the same network
- You can set any destination address and amount you want, and even any asset as long as it's on the same network (for example, if you sent an Ethereum token, the new transaction can send the same token on Ethereum, a different token on Ethereum or pure ETH). All values set here will overwrite the pending transaction. You can send 0 ETH to to your own address for example if you no longer want to send anything anywhere.
- Expand the "Advanced Settings" menu
- Set the nonce value to the one noted on step 2 and continue. Do not change the gas limit.
- Send using a higher gas price than the transaction you're trying to replace
- The transaction with highest gas price will confirm first, and all others with the same nonce will become invalid, showing as "Replaced"
Multiple unconfirmed transactions
On Ethereum and EVM chains, transactions must confirm in ascending order of nonce value. The default behavior of Koala Wallet is to automatically increment the nonce of new transactions every time one is sent. If you have multiple pending transactions, the ones with higher nonce values will remain pending until all lower nonces have confirmed. If your first transaction used low fees and subsequent transactions used high fees, after the first replaced transaction confirms, the others may confirm immediately afterwards.
You can read more about the advanced settings and what the "nonce" is here.
Blockchain immutability and security
By definition, unconfirmed transactions are not yet on the blockchain. Being able to alter an unconfirmed transaction does not change or break the immutability of blockchains. If the network returns to a low fee environment, the original transaction may confirm before you have the chance to replace it with one with different attributes. The process described above will definitely not work after the transaction confirms.
It's only possible to replace transactions that you sent yourself. You cannot replace transactions sent by others even while unconfirmed.