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 ...
Raghav Sood's user avatar
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-...
G. Maxwell's user avatar
  • 7,727
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 ...
morsecoder's user avatar
  • 14.2k
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 ...
Fernando Gutierrez's user avatar
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 ...
David Schwartz's user avatar
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Here is the list of known sources of malleability from BIP62 (which has been withdrawn, and is no longer up to date, but does give some insight): DER encoded ECDSA signatures Right now, the Bitcoin ...
Pieter Wuille's user avatar
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....
Pieter Wuille's user avatar
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 ...
Murch's user avatar
  • 75.2k
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, ...
m1xolyd1an's user avatar
  • 5,636
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 ...
Murch's user avatar
  • 75.2k
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&...
MCCCS's user avatar
  • 10.2k
5 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 ...
Vojtěch Strnad's user avatar
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 ...
Nick ODell's user avatar
  • 29.4k
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 ...
David Schwartz's user avatar
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 ...
Christer's user avatar
  • 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 ...
Nate Eldredge's user avatar
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-...
chytrik's user avatar
  • 18.3k
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 ...
Pieter Wuille's user avatar
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 ...
Nate Eldredge's user avatar
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 ...
UTF-8's user avatar
  • 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 ...
Claris's user avatar
  • 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 ...
chytrik's user avatar
  • 18.3k
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 ...
Raghav Sood's user avatar
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 ...
RedGrittyBrick's user avatar
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 ...
Ugam Kamat's user avatar
  • 7,408
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&...
Murch's user avatar
  • 75.2k
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 ...
Murch's user avatar
  • 75.2k
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 ...
Pieter Wuille's user avatar
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 ...
leevancleef's user avatar
3 votes

Did Satoshi invent UTXOs?

If you read about Hal Finney's Reusable Proof-of-Work (RPOW), you'll see many similarities to UTXOs. RPOW was a prototype network where individuals created tokens using a similar PoW system to the one ...
Sachin Meier's user avatar

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