23
votes
Accepted
Why is there "Change" in Bitcoins?
Bitcoin follows a Unspent Transaction Output (utxo) model.
Our modern banking systems follow an account model - you're assigned a bank account number (similar to an address), and send and receive ...
- 16.9k
19
votes
Accepted
If bitcoin is indivisible, where does change come from?
I like to suggest a mental model where the network is a metals forge:
You have a 1 oz gold coin stamped with your key on it, with your transaction you send it to the forge to be melted down and re-...
- 7,696
17
votes
What does change address mean inside Electrum wallet?
Receiving addresses are addresses generated specifically for sharing with people to send payments to you. Change addresses are generated by your wallet automatically when you send funds to someone ...
- 14k
12
votes
Accepted
Why is the change address for a transaction the same as the originator address?
Many wallets let you control where to send the change. In most cases it is advisable to send to a new address to reduce traceability and increase your privacy a little, but not everyone does and ...
11
votes
Why is there "Change" in Bitcoins?
There are a lot of good answers, but I want to point out the most obvious answer.
Say you have 1 bitcoin and you send 0.2 bitcoin to me and the design leaves it so that you still have 0.8 bitcoin in ...
- 51.4k
9
votes
What can be changed in signed bitcoin transaction?
Here is the list of known sources of malleability from BIP62 (which has been withdrawn, and is no longer up to date, but does give some insight):
DER encoded ECDSA signatures Right now, the Bitcoin ...
- 102k
7
votes
If bitcoin is indivisible, where does change come from?
I'm adding this as an additional answer to the ones that exist, to clarify a comment:
if the outputs can be split exactly, then why the inputs can't be split so I only spend the exact amount I want....
- 102k
6
votes
Accepted
Why are there round numbers after the fees and no change?
If your wallet has a large UTXO pool with some variance in the values, it is often possible to find a combination of inputs that provide a matching amount to pay for recipient output and transaction ...
- 72.6k
5
votes
If bitcoin is indivisible, where does change come from?
It's not the value, it's the inputs. If you have 1 input worth 1 BTC and sent Alice .22 BTC as one output and your change would be a 2nd output. A single input can be split into many outputs. If Bob, ...
- 5,596
5
votes
Accepted
Where is the change from the output stored in?
When a sender creates a transaction, they explicitly define which pieces of bitcoin they spend. We call such pieces of bitcoin Unspent Transaction Outputs (UTXO) and you can think of the UTXO set as ...
- 72.6k
5
votes
Why is there "Change" in Bitcoins?
And if so, why don't you just send 0.4 BTC in the beginning?
Bitcoin was designed to allow single-in multi-out or multi-in multi-out payments. In Ethereum, only one address fills the whole "to&...
- 10.1k
4
votes
Why is the change address for a transaction the same as the originator address?
Bitcoin Core sends change to a different address, but the Bitcoin protocol does not require that. You can write a Bitcoin client that sends the change to the original address.
There's no benefit to ...
- 29.3k
4
votes
Accepted
When a block that has a transaction with change in it is successfully mined, is the change transaction included in the newly mined block?
There is no change transaction type.
Transactions are defined as a list of inputs consumed, and outputs created, and the values assigned to those new outputs. The creator typically makes an output ...
- 15.4k
4
votes
Accepted
Why do transactions send coins to the same address as they spent it from?
Likely the sender didn't have an unspent output that had exactly the amount he wanted to send. So he choose an unspent output that had enough and sent the remainder back to himself.
Accounts do not ...
- 51.4k
4
votes
If bitcoin is indivisible, where does change come from?
The bitcoins themselves never really exist, only receipts from previous transactions. So if received that 1 BTC from a friend, you have a receipt somewhere saying that he sent you 1 BTC. You can then ...
- 141
4
votes
What happens when two transactions send to the same address?
It works just fine.
Bitcoin transactions can have multiple inputs and outputs; each input is a "pointer" to an output of a previous transaction (specifically, it consists of a transaction id and ...
- 23k
4
votes
Why is there "Change" in Bitcoins?
There are some good answers here, but I'm surprised nobody has mentioned privacy.
Having coins sent to a new change address can improve your privacy in many ways. Consider this simple example: a one-...
- 18k
4
votes
Accepted
How do I perform a RBF transaction through Bitcoin Core?
If you're using the GUI, head over to the "Transactions" tab, right-click the pending transaction and choose "Increase transaction fee". If you're using bitcoin-cli, use the ...
- 6,733
3
votes
Accepted
Why did the remaining money go to another address?
What you are observing is a change address.
The wallet created a new address for itself to send the change of spending the 1 BTC to. This is so that it is non-obvious to the rest of the world which ...
- 102k
3
votes
Accepted
Anonymity of Bitcoin ownership a fakery?
Bitcoin isn't anonymous in any rigorous sense, and the developers never claimed it was. See for instance https://en.bitcoin.it/wiki/Anonymity. If someone has been telling you that it is, then indeed ...
- 23k
3
votes
Accepted
Why does coinbase make 2 transfers instead of one
When you receive money, a UTXO (unspent transaction output) is generated and assigned to your address. When you want to spend money, you can only ever spend entire UTXOs. However, you may have ...
- 3,224
3
votes
Accepted
Seemingly random transactions on testnet
Testnet is generally pretty noisy, filled with strange transactions and nonsensical movements of money. I personally hold wallets responsible for 20%+ of all transactions in the block chain, and most ...
- 15.4k
3
votes
Determine which transaction output is a change address and which is not
You can guess at which output is a change address, but the only way to be certain is if you are the person initiating the transaction.
In fact, some wallet software could be designed to ...
- 18k
3
votes
Accepted
Determine which transaction output is a change address and which is not
This is usually (intentionally) not possible.
Well designed wallets attempt to obfuscate the change vs. non-change addresses to make it harder to find out which part is the payment for privacy ...
- 16.9k
3
votes
Bitcoin core wallet - got 0 balance after transaction
The second output is most likely change being returned to your wallet. Just like when you use a $5 banknote to buy a $1 item. You get $4 back in change. You don't try to tear off 1/5th of the $5 ...
- 25.2k
3
votes
Accepted
Is a bitcoin UTXO divisible?
Is this true?
Yes, it is true. In very very simpler terms, think this to be in a way wherein someone sends you a coin worth that amount. In other words, if someone sends you 10 BTC, they are sending ...
- 7,348
3
votes
Accepted
How is the UTXOs of each partially-spent TxIn determined?
a transaction (Tx) can have multiple inputs (which are previous unspent transactions = UTXOs), let's call them the TxIn
More accurate would be to say "unspent outputs from previous transactions&...
- 72.6k
3
votes
I somehow sent a transaction to my own wallet address
Welcome to Bitcoin. The "balances" in Bitcoin are actually explicitly tracked bits and pieces. You can think of it akin to the coins and bills of cash: when someone sends bitcoins, the ...
- 72.6k
3
votes
How does change address interact with original address
There is no relation at all between the two addresses, except that they're owned by the same person/wallet.
At the protocol level, "change" does not exist. It's just another output (with a ...
- 102k
3
votes
Accepted
Can you have a transaction without a change output?
Yes, absolutely you can. I think the article intend "the simplest case" in the real world usage, where is highly unlikely that you have to pay the exact amount of one of your UTXO, if not ...
- 862
Only top scored, non community-wiki answers of a minimum length are eligible