This question comes up a lot in a wide variety of formats and cases, so I'll go one by one in order of complexity:
I sent X Ether from a wallet or exchange and it hasn't arrived on my computers wallet , it's been - - X Minutes - - !
Answers / Solutions :
Your Ether is on it's way, the network is congested or your wallet confirming the transaction, your exchange or wallet could also be having a delay, so the solution is to just wait.
How long should a transaction take ?
Ideally about 1 minute, the blockTime target is around 20 Seconds and the Block Wait is 3 Blocks, so 60 seconds. In order to see the current wait time please consult a block explorer like one of the following.
I sent X Ether from a wallet or exchange and it hasn't arrived on my computers wallet, it's been - - X Hours/Days - - !
Answers / Solutions :
Something needs your attention but you might just need to wait longer.
The first thing to check is your transaction Hash (also called transaction ID, transaction Receipt or simply receipt ), which is a long number that identifies your operation on the blockchain and helps diagnose what went wrong, it looks like this:
Just search your transaction by pasting your txHash into the block explorer, here's what a successful transaction looks in Etherscan:
Solutions ( In order of complexity ) :
If your transaction was successfully processed by the Ethereum Blockchain, the most likely reason you are not seeing your funds is because your Wallet is not yet synced to the Blockchain. Syncing your wallet should resolve this issue.
If you need immediate access to the funds or can't access your wallet, you might need to open an online wallet ( or a faster wallet) by importing your account and private keys ( If you don't have this information or didn't backed it up you might not be able to).
You don't have your private keys but have access to the computer where the wallet was installed. In some cases/wallets you can import/export your keys directly from your hard drive into an online wallet where you will have access to your funds, procedure varies by wallet ( some don't provide the functionality ) and you need to be careful (backup your keys / files,store them securely and do not share them) The first option, syncing your original wallet is the preferred way.
HELP ! My transaction is stuck !
Due to how mining and the Ethereum blockchain works, your transaction might get stuck in a pending state, it might be there for a long time in limbo, usually a day or 2 and the txHash might even disappear at some point ( the transaction gets dropped ) without you receiving your ether, this is what it looks like:
Note that sometimes your transaction might be reported as missing by one block explorer, try other block explorers to confirm that it exists.
Solutions
Transactions usually get stuck due to your transaction providing a low gas price during high network activity periods.
If you are unsure about what gas is please review this explanation from the MEW wallet:
One solution is to just wait, ( sometimes up to a few days ), your transaction will either go through or be dropped, in the later case you will have to resubmit your transaction. Further, if gas conditions are still high you will need to offer a better gas price.
Remember that you as user are in charge of enticing miners to process your transactions by offering them fees, so your low offer might or might not be processed due to how little incentive ( in gas form ) you offered.
You need your funds sooner...
In this case you will need to first cancel your transaction, and only after your transaction has been recognized as canceled by the blockchain (minutes to hours), you will then need to resubmit your transaction. You might need to increase your gas price if the network is still congested.
How much gas to offer ?
Good question !
Gas price is always changing depending on network conditions, ideally your wallet or exchange should provide a good gas price, but sometimes you have to increase it manually, you can take the gas price estimates from https://ethgasstation.info
In general your gas limit should be the same as the one your exchange or wallet is providing, usually 21000 for sending a transaction or transferring Ether.
HELP ! I've made a mess of transactions !
The story goes like this, your first transaction fails due to low gas, you send a higher gas one, but since the first one is still pending, it won't allow the second one to process, then you send a 3rd or fourth in desperation, you get duplicate error and nothing seems to happen, while in the background you have an ever growing number of stuck transactions.
Solution
You need to cancel each and every transaction that you have made,(process varies by wallet ) then you need to wait ( usually a few hours ) so the blockchain clears those canceled transactions; ( you can ask multiple block explorers to see your account to troubleshoot )
and then send a new transaction with a higher gas price.
If none of this works for you, your next option would be to send raw transactions, this is an advanced topic so hopefully you won't have to go there and beyond this troubleshooting guide.
Help my transaction failed or has an error
One last case we should mention is when your transactions fail, these are usually calls to a contract rather than just Ether transfers, and they look like this in Etherscan:
Your wallet or exchange should also tell you your Transactions failed and why.
Transactions fail for a number of reasons, running out of gas and bad instructions are common, in some cases you lose some or all the gas you send along, so they can be costly.
Solution.
If you are getting this type of errors, you need to make sure that you understand how you are interacting with a contract, the provider of the contract should give you clear instructions on how to call it. Once you know this, you will need to send another transaction with the correct information or gas limit.
Check is in the mail !
I tried covering most of the usual cases, but feel free to comment with your particular case if it's not mentioned.
I should also mention that I am not officially involved with the Ethereum Foundation or project, although I am very involved with the technology as a developer.
If you liked this article or it helped you, please upvote it !
Thanks !
Keno
Shameless plug: If you are looking for an introduction to Ethereum, Solidity and Smart Contracts I just published an eBook and print Book on getting started:
