How output transaction works in Bitcoin?

Note also that an output can be used only once. That's why there's a concept of "change address" in the bitcoin ecosystem: if an output of 10 BTC is available for me to spend, but I only need to transmit 1 BTC, I'll create a transaction with two outputs, one with 1 BTC that I want to spend, and the other with 9 BTC to a change address, so I can spend this 9 BTC with another private key that I own.

So what will happen if an output of 1 BTC is available for me to spend, but I want to spend 10 BTC?

Note: It is a general question and is not specific to any API feature.

So what will happen if an output of 1 BTC is available for me to spend, but I want to spend 10 BTC?

If you have 1 USD in your pocket and you want to buy something for 10 USD, you simply can't.

The cited section is equal to: If you have 10 USD and want to buy something for 1 USD the merchant gets 1 USD and you get 9 USD in change.

• Oh! So the output value is your account balance! Thanks a lot! :D Jul 13, 2018 at 13:13
• @Gagan worth mentioning: in bitcoin there is not an ‘account balance’, there is only UTXOs (unspent transaction outputs). So your wallet’s ‘account balance’ is simply the sum of all UTXOs your wallet controls. As related to your Q: to spend a UTXO is to ‘consume’ it entirely. You cannot just spend ‘half a UTXO’, it is all or nothing (hence the reason a change address exists, so you can pay yourself back any excess funds in the UTXO). Other cryptocurrencies use an ‘account balance’ system, the difference seems subtle, but it is important if you want to understand these systems. Jul 13, 2018 at 19:31

So what will happen if an output of 1 BTC is available for me to spend, but I want to spend 10 BTC?

You would have to create a manually crafted transaction, and instead of 1 BTC you make it a 10 BTC. Then the network rules come into play, and when you forward the transaction it is checked for validity. The rule 14 specifically, but also 9,12 and 15 would apply, making the transaction invalid.

• Thanks for the approach! That's great for learning how network rules play. :) Jul 13, 2018 at 13:17