Bitcoin Forum

Whenever I send bitcoin, I see two addresses as recipients. For example, see this transaction

https://blockchain.info/tx/cbdc112a33125480fa539911c3cc6f4eea5fa7c34b2df895e6de058f204a8794

The address with "1F" is where I sent 10BTC to. What is the "1AvH" address? That address is somehow related to my wallet?

It's most likely the "change"

Transacitons have numerous input and outputs.

The sum of all the inputs must equal the sum of all the outputs.

The money you have available is the sum of all your available inputs (they're actually outputs from previous transactions - AKA Unspent Transaction Outputs or UTXOs)

You can't divide UTXO without sending it through a transaction like what's happened there. For example:


So say you have 10BTC in 1 UTXO, and you want to send someone 5BTC, you put 5BTC in you client and press send

Behind the scenes, you client only has 1 UTXO to play with which is 10BTC, so you have to use that as in input.
So the transaction has 10BTC input, and 5BTC output to the person your paying.
In that state, the total input is 10, total output is 5, so they don't match up, your money disappears.
To solve this, a "change" output is added: basically the remaining 5BTC that isn't going to your friend is sent back to you as an extra output.

The position and address used for the change output is randomised by the client to protect anonymity a bit more.

Hope this helps:)

Thank you so much! I had a momentary freak out when I saw the other address. This explanation helped me. +1 karma for you.