These methods are only advised for expert users who have a good understanding of the way blockchains work. Canceling or replacing a transaction is not guaranteed to work, and may lead to additional stuck transactions.
The cancel/replace method is only available with the use of MEW offline and only for software access methods (keystore file, private key, or recovery phrase). You can't use this method with a hardware wallet, browser wallet, or mobile wallet (unless you use the recovery phrase directly which is NOT recommended for the security of your wallet).
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Can I cancel, replace, or do anything once a transaction has been sent?
Most of the time, the answer is no.
Once a transaction has been mined and included in a block on the blockchain, it cannot be canceled or replaced.
During times of normal volume, transactions are mined within seconds and do not spend any length of time in the transaction pool. There is simply not enough time to cancel, replace, or override a transaction once it has been sent.
However…
During times of extremely high volume and high gas prices, transactions could be pending for hours or days before being mined.
If your transaction is pending for a seemingly infinite amount of time, you could try to replace it with a new transaction.
The easiest way to do this is by sending a 0 ETH transaction to your own address with the same nonce and a higher gas price. This will cancel out your first transaction.
There is no guarantee this will work, nor that it will work every time. You may end up adding more stuck transactions if you don’t follow the process carefully, and even then there is no guarantee.
This article is NOT saying that you can cancel a transaction you accidentally sent to the wrong address, or that you can get your ETH back once it has been sent.
It only pertains to finding, checking, and potentially replacing transactions that have been stuck in the transaction pool for a very long period of time.
How to Check the Status of a Transaction
Step 1. Head to an Ethereum blockchain explorer, like Etherscan.io, Ethplorer.io, or EthVM.
Step 2. Copy and paste the transaction hash into the search field provided.
Step 3. Details will appear depending on the state of the transaction. It will say:
Success: Your transaction was successfully mined and is on the blockchain.
If you do not see any errors, your transaction was successfully sent. Your ETH or tokens are where you sent them. If this balance has not been credited to your wallet or exchange account 24 hours after sending, please contact that service. Send them the link to your transaction and ask them to look into your situation.
Failed:
If you see a red ( ! ) symbol, or a “BAD INSTRUCTION” or “OUT OF GAS” error message, it means that the transaction was not successfully sent. You cannot cancel or replace this transaction. Instead, send a new transaction. If you received an “Out of Gas” error, you should double the gas limit you specified originally.
If you see ‘Reverted’, it’s a good idea to double-check the actions you’re taking. This is an error having to do with a smart contract user error.
Transaction Not Found: This transaction cannot be found. It’s possible that it did not go through, or that it cannot be found in the Ethereum blockchain explorer you are using. Try using the other one (Etherscan.io, Ethplorer.io, or EthVM). If you still can’t find it, it never went through.
Pending: Your transaction was located in the transaction pool of the explorer you are using. It is currently pending (waiting to be mined). There is a chance you can cancel or replace this transaction, but it’s a very small chance.
If your transaction says ‘Pending’, check the gas price you used for this transaction and compare it to the gas prices seen on Etherscan's gas tracker. If it’s much lower than the ‘Low’ price listed, then you have a good chance of replacing or canceling it.
“Replacing” vs “Canceling” Transactions
Canceling: This is when you want to ‘undo’ your transaction. You don’t want it to go through, so you generate a
0 ETHtransaction to your own address with the purpose of preventing a previous transaction from “going through” / “being mined” / being included in the blockchain.Replacing: This is when you want your same transaction to go through faster, or you want to replace it with another transaction. You generate a
XX ETHtransaction to someone else’s address with the purpose of doing something (i.e. sending funds, revealing an ENS bid, etc.) while simultaneously not having a previous transaction go through.
The reason we recommend ‘Canceling’ over ‘Replacing’ is that it is not guaranteed your second transaction will actually replace your first one. Choosing to replace a transaction with a new one could lead to more confusion, headaches, and pending ETH, or ETH spent unnecessarily in the form of gas. This is especially true if your first transaction is mined anyway, which is possible.
Canceling a Transaction
Canceling means generating a 0 ETH transaction to your own address with the purpose of preventing a previous transaction from “going through” / “being mined” / “being included in the blockchain” / “being stuck”.
Step 1. Head to Etherscan.io, Ethplorer.io, or EthVM.
Step 2. Paste your transaction hash.
If it says pending, you can still try to cancel it.
If it says not found, click the button again, waiting a few minutes between each click. If that doesn’t work, it’s likely your transaction never went through.
If it says success, you cannot try to cancel it.
Step 3. If it says pending, make note of the ‘Nonce’ being used by the transaction, you will need it later.
Step 4. For the rest of the process, you will need to use MEW offline. See the following article for instructions on downloading and using MEW offline to generate transactions.
Step 5. Using the MEW offline method described in the link above, generate a transaction to your own address with a balance of 0 ETH, a high gas price (reference Etherscan's gas tracker to get an idea of a high enough price), and use the same nonce you noted from step 3.
Keep in mind, the higher the gas price, the higher the transaction fee (Gas Limit * Gas Price).
Step 6. You will receive a new transaction hash. Search it on the blockchain explorer of your choice and see if it posts as successful. If done correctly, your pending transaction should be gone and instead replaced by a successful transaction for 0 ETH, sent to yourself.
Replacing a Transaction
Replacing a transaction means generating a XX ETH transaction to someone else’s address with the purpose of doing something (i.e. sending a transaction, revealing an ENS bid, etc.) while simultaneously not having a previous transaction go through. This can be the same transaction as the one that’s pending or a completely different transaction.
Step 1. Repeat steps 1 - 4 from the ‘Canceling a Transaction’ section above.
Step 2. Fill the ‘To Address’ field with whatever address you wish to send to.
Step 3. Using the MEW offline sending process, generate a transaction with the token and amount you wish to send, a higher gas price, and the same nonce as the pending transaction.
If you are sending a standard ETH transaction, you can use
21000for the gas limit. If sending tokens, raise it to around100000.Keep in mind, the higher the gas price, the higher the transaction fee (Gas Limit * Gas Price).
Step 4. You will receive a new transaction hash. Search it on the blockchain explorer of your choice and see if it posts as successful. If done correctly, your pending transaction should be gone and instead replaced by the successful transaction of your chosen amount to your chosen address.
Notes on gas fees
MEW does not receive any transaction fees. They are necessary for the blockchain to work and include your transaction in a block. The fees are paid to validators supporting the network.
To learn about gas fees, see this article: https://help.myetherwallet.com/en/articles/5878945-what-is-gas
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