Unspent Transaction Outputs (UTXOs) are created by transactions and allow the owner of an associated address to spend a specific amount.
Questions tagged [utxo]
288 questions
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What is an "unspent output"?
What is the meaning of the term "unspent output" in the Bitcoin protocol?
ripper234
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How is a wallet's balance computed?
I am wondering on how a wallet's balance is computed. Basically, from what I've read I assume that you look back at all transactions involving all the keypairs of a given wallet. Adding up all the transactions' balances (negating a transaction…
marcus
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How big is the UTXO database?
Is there a query that will return the size of the UTXO database? Specifically, the total number of unspent outputs.
pinhead
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UTXO model vs. account/balance model
I understand that Bitcoin uses unspent tx output and Ethereum account balance based. However, recently there are lots of discussions on that Bitcoin's UTXO database has become too big. Does this mean account balance based transactions are better in…
Yangrui
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Where is the UTXO data stored?
When a new transaction is received it is added to the memory pool (after checking for conflicts). While mining, only the transactions which are in the pool are considered. What happens to the transactions after they are included in a newly mined…
somesh
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Why is there "Change" in Bitcoins?
I have read about a change address and wondered why there even is the concept of change?
Let's say I received 1 BTC from some person A and I want to send 0.4 BTC to another person B, afterwards. From what I have understood, I have to send the 1 BTC,…
André Kuhlmann
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Why does Bitcoin store all transaction inputs and outputs, instead of just an "account/balance" ledger?
From what I can tell, the Ethereum blockchain just stores accounts and balances - why did the original Bitcoin developers choose the method of storing all transactions for validation instead of just account balances? It seems like that would reduce…
pinhead
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With 100% segwit transactions, what would be the max number of transaction confirmation possible on a block?
With 100% segwit transactions, what would be the max number of transaction confirmation possible on a block?
And, how many utxo can be updated by a block full of segwit transactions?
vi.su.
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Why is Bitcoin Core using LevelDB instead of Redis or SQLite?
Why did Core move from BDB to LevelDB? Why don't they use SQLite or move to Redis now? Is there a technical reason for this choice?
Etherkimist
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Why do outputs need to be spent entirely?
I understand what change is and how it works (and it's analogous to physical money change), but what I don't understand is why this is needed in the first place.
Given that this is all computer based, I thought that money could be sent just by…
Arturo Torres Sánchez
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What are the main technical hurdles to implementing UTXO commitments?
Commits of the UTXO set in the block header would enable more secure lightweight clients and caps on the number of blocks that need to be downloaded and validated in the Initial Blockchain Download, which is vitally important for Bitcoin's longevity…
Amin
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Why is there no such thing as a redirected, forged, or fake transaction?
In the past, we had numerous questions about "fake" or "forged" transactions. Such transactions could supposedly be created even without holding any bitcoins, yet would end up in the mempool or even get accepted by the network once they are mined…
Murch
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Transaction with Multiple Inputs having Same Address
Why do transactions have multiple inputs with the same address? Is it because the amounts were obtained in the address through multiple separate transactions. Shouldn't the amounts be clubbed to a single input since the addresses are the same. An…
Ni9elF
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What are the trade-offs between the different algorithms for deciding which UTXOs to spend?
When someone would like to make a transaction, their software has to choose which of their UTXOs to spend. Here are a few different ways that one might prioritize which UTXOs get spent.
Oldest UTXOs first
Newest UTXOs first
UTXOs with the smallest…
morsecoder
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Can the outputs of transactions with duplicate hashes be spent?
I've noticed that there are two transaction hashes that appear more than once in the blockchain. The reason for this is understandable: they sent mining rewards to the same address. These transactions had the same inputs (none) and the same outputs…
Mike
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