Inputs and outputs – Bitcoin “change” explained

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Last updated on March 18th, 2015 at 10:42 am

Did you ever try to send out Bitcoins and found out that a larger amount than what you intended seemed to be sent ? Here’s an explanation why this happens…

The blockchain is a big file that keeps track of all Bitcoin transactions ever made. So if you own some Bitcoins, all it means is that the blockchain has references to transactions that were made to your Bitcoin address. The term for these references is “Inputs”.

Now let’s say you enter a store to buy a watch for 1 Bitcoin. instead of taking out actual cash from your pocket and paying for something you just tell the seller – “here are the references that I have this money” or “here are my inputs”.

What you mean is – here are previous transactions sent to me that add up to 1 Bitcoin or more. This is called an output, so each output is compiled out of 1 or more previous inputs.

Once you use an input to pay for something it is considered “spent” and you can’t use it again for other outputs. So in this case once your output is confirmed it will become an input for the seller to use in future transactions.

Bitcoin rules state that you can’t use just a part of an input. So if for example I wanted to send the seller 1 Bitcoin and the only input or reference I have is from someone who previously sent me 1.5 Bitcoins I will have to use all of this input and return the “change” back to my original address as a new input. So I will use my 1.5 Bitcoins input, pay 1 Bitcoin to the seller, pay a miner’s fee and return the rest to my original address.

Now for a real live example – if you examine the inputs closely you will see that the output consists of an input of 0.142 Bitcoins. 0.005 Bitcoins were sent to someone else, a miner’s fee of 0.0001 Bitcoins was deducted and the rest of the money was sent back to the original address.

That’s why you’ll sometimes see additional coins sent with your transactions. These coins will be sent back to your change address which you can configure manually inside your wallet.

If you want to inquire more on specific inputs you can enable “advanced” mode in Blockchain, track inputs and see which inputs have been spent or not.

Ofir Beigel

Owner at 99 Coins ltd.
Blogger and owner of 99Bitcoins. I've been dealing with Bitcoin since the beginning of 2013 and it taught me a lesson in finance that I couldn't get anywhere else on the planet. I'm not a techie, I don't understand "Hashes" and "Protocols", I designed this website with people like myself in mind. My expertise is online marketing and I've dedicated a large portion of 99Bitcoins to Bitcoin marketing.
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27 Comments on "Inputs and outputs – Bitcoin “change” explained"

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Maggie
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Maggie
HI! I a beginner and i have a question . I use Coinbase and Bittrex, Isent BTC from coinbase to bittrex and never came into me wallet. On coinbase transaction shows completed but on Bittrex i did not even recive a pending deposit. Now when i do go into Blockchain info i do see my transaction but i also see another transaction as if btc was going out of my wallet? What happened to my BTC. I do not understand that. And how can i get it back? Please help me. I already lost some money before and i cant… Read more »
Zsofia Elek
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Zsofia Elek

Hi Maggie, if you have the transaction ID I suggest you follow up with that with the Coinbase and Bittrex support teams and ask them about the details. Bitcoin change can be an explanation for the outgoing transaction, but it would worth double check that your account hasn’t been compromised

Rabinovitch
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Rabinovitch

The video is unavailable. “This video is not authorized to be embedded here.” Please do something.

Zsofia Elek
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Zsofia Elek

Hi Rabinovitch, I see no problem with the video. Which browser do you use?

Ethan Hernandez
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Ethan Hernandez

Thanks for sharing, this was super easy to understand, I think I’ll give Bitcoin a try.

Noah Jones
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Noah Jones

I know thousands and thousands of people rely on Bitcoin but for me it sounds like sorcery! I’m not bashing it or anything but we got so used to real money that it sounds soo strange!

Ofir one
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Ofir one

So did the Internet when it first started..

Jay Morgan
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Jay Morgan

People are quick into judging and labeling everything they see before actually giving it a try. Some of my friends immediately began saying Bitcoin is a scam and I would get homeless if I decide to change some of my investments in bitcoins. This is downright silly and this is the reason why few are getting richer and richer while most of us are in huge debt: if you don’t take a chance and decide to go against the wind you won’t amount to anything.

Anette Cecilie
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Anette Cecilie

The video is pretty straightforward, I hate it when people use very economical terms to explain how Bitcoin works.

Ofir one
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Ofir one

Thank!

William Silva
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William Silva

I recently started reading about Bitcoin mining and I was also checking your guide, Ofir, and it answered all my questions, thanks!

Ofir one
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Ofir one

You’re welcome, thanks for the feedback

John Matthews
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John Matthews

I was a bit eerie about Bitcoin at first; just when I decided to invest some money in this I started reading about how Governments don’t like the fact that it’s unregulated and they don’t have any control over it. This was a huge bummer and made me lose my enthusiasm. Do you think worldwide economical forces could take over Bitcoin and make it theirs?

Ofir one
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Ofir one

Bitcoin doesn’t belong to anyone, so governments can take over it. They can try and regulate it but it’s more a matter of supply and demand in my opinion. Even if a country bans Bitcoin entirely people will still be able to trade it semi anonymously.

Stephen Segura
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Stephen Segura

Bitcoin seems to be everywhere lately! I had absolutely no clue how to use it and if it’s worth using it. I’m not one to jump head first into new trends so I had to do my research first. You have tons of knowledgeable and easy to understand videos, thanks for providing these resources for free.

Ofir one
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Ofir one

You’re welcome, thanks for the feedback!

Jason McIntyre
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Jason McIntyre

One of the best things about Bitcoin is the fact that there’s no currency converter; a Bitcoin has the same value, regardless of your country and currency. I use it from buying food and clothes to electronics; I bought my girlfriend a Dell laptop directly from their site. The future clearly belongs to digital currency!

Ofir one
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Ofir one

Well I guess it depends on how you look at it. In the future there will indeed be no currency convertor but today people still attach Fiat value to Bitcoin whenever they purchase something.

Samantha Rotterns
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Samantha Rotterns

What I love most about Bitcoin is that everything is done anonymously. There’s no need to publicly share your name or other personal details, only your wallet ID will be made public after the transaction is done. I know, I know, bitcoins are used by drug dealers and people that don’t want the transaction being traced back to them, but no currency is PERFECT.

Ofir one
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Ofir one

Indeed Bitcoin is the best version of cash you can get today

shawnread
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shawnread

1 BTC > 1 USD > 1CAD > any other currency. So yeah lol.

Michael Towner
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Michael Towner

I absolutely loathe banks and their outrageous commissions and fees. I joined the Bitcoin train two years ago and it was the best decision I ever made. A bitcoin is right now worth $586 and while it may be considered stagnant by some, I can bet you it will start growing in the near future and become more and more popular.

shawnread.ca
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shawnread.ca

I agree but the fat cats doing all the mining are ruining the purpose of BitCoin, to have no single centralized bank. Now you got even some warehouse full of raspberry pies makin a million a day, you cant compete with there hashing power, probably obtained from the money they initially made.

Ofir one
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Ofir one

I agree as well…won’t stay at $580 for long

Vlad Nistor
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Vlad Nistor

Or it could go lower.

Ofir one
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Member
Ofir one

True, but from what I’ve seen in the past year and a half dealing with Bitcoin I believe that in the long run it will only increase in value.

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