Bitcoin Forum

Hello,

Where can I find the number of UTXOs my receiving address contain ? Is there any website ?

If I reuse an address to receive bitcoin will it count as a second UTXO ?

Thanks,

You can see that on blockchain explorers, like blockchair.com. You can be able to see your UTXOs on most wallets too. But to make it easy, use wallets with coin control. Wallets like Electrum and Bluewallet.

Yes. If you use an address to receive bitcoin two times and you want to spend the coins or part of the coins from first and second UTXO, it will have 2 inputs and the more the fee.

To be able to spend from certain UTXOs of your address or of your other addresses, use a wallet that has coin control.

To get the number of UTXOs (Unspent Transaction Outputs) contained in your Bitcoin receiving address, you can use a blockchain explorer.  Blockchain explorers are websites that allow you to explore and view detailed information about the blockchain, including your Bitcoin addresses.

 Some popular blockchain explorers you can use are:

 Blockchain.com (https://www.blockchain.com/)
 Blockchair (https://blockchair.com/)
 Bitcoin.com Explorer (https://explorer.bitcoin.com/)

Regarding your second question, if you reuse the same Bitcoin address to receive funds, each received transaction will be treated as a new UTXO.  UTXOs are not automatically combined when receiving multiple transactions to the same address.  Therefore, if you receive multiple transactions on the same address, there will be multiple UTXOs associated with that address.

In the tab Coins in Electrum and in the tab UTXOs in Sparrow wallet I have only one UTXO
However on the website blockchain.com it's written output count 4 and unspent output count 1
Is ist normal ? What's the difference between output count and unspent output count ?

There are two types of transaction outputs if we apply classification based on their status: unspent transaction outputs (UTXOs) and spent transaction outputs (as far as I know, this type didn't get a well-established acronym, but we can call it "TXOs" for short.) Your wallet shows only UTXOs in the "Coins" tab because it has corresponding private keys to them and manages all information necessary for transaction signing and broadcasting. On the other hand, TXOs have already been used and spent to the addresses to which your current wallet has no private key. It still may show these outputs in the transaction history, but it is mainly for user experience. Please note that not all wallets can show UTXOs as a separate list of selectable items: this feature is known as "Coin control" - a privacy-enhancing technique aimed at giving users more control over addresses and transactions.

More clearer !
So regarding a future transaction I should only take into account UTXO and not TXO right ?
Fees will be determined by UTXOs
Any idea how minimum satoshis should a UTXO contain in order to be spendable so that fees don’t exceed the UTXO balance ? maybe fees in the future will be so high ?

Yes. UTXOs are the bitcoin that you received and that you can spend.

Fee is determined by the UTXO count. Assuming you send bitcoin to someone, and the UTXO count is 3 (I mean the transaction input is 3 in the coin you are sending), that means you will pay more. The more the count the more the fee. But not only that, the more also the transaction output (the addresses you are sending to), the more the fee, but lesser in fee than to send each time to the addresses differently.

Dust limit for legacy address is 546 sat. If it is native segwit, it is 294 sat. But why thinking about dust limit because the value is very small and not worth discussing. But some people use it for dust attack to trace certain coins.

UTXOs can be used as inputs for your transactions. Your transaction fee will be decided by transaction size and fee rate. Transaction size depends on your input number (more inputs, bigger size) and your address types.

https://jlopp.github.io/bitcoin-transaction-size-calculator/
https://bitcoinops.org/en/tools/calc-size/
https://bitcoindata.science/plot-your-transaction-in-mempool.html

You have to check mempools to use good fee rate.
https://mempool.space/
https://jochen-hoenicke.de/queue/#BTC%20(default%20mempool),24h,weight

This Telegram bot Bitcoin Fees - fees and tx tracker (https://bitcointalk.org/index.php?topic=5445635.0) gives you good notifications.

Fees are not forever cheap or forever high. Mempools can change with time so does transaction fee.

When fee rates are cheap, consolidate your small UTXOs (https://bitcointalk.org/index.php?topic=2848987.0)

Both inputs and outputs of a transaction contribute to the "weight" of a transaction and thus the required transaction fee. Usually the inputs of a transaction contribute more to the weight than the outputs. Also the address type used particularly for the inputs plays a role on the weight of a transaction.

I have a noob question but if I reuse an address it will create a new utxo right ? So I will have two utxos in the same address ?

Yes.

You asked this question before:


Now you ask this:


Have you been reading what people are posting on in this thread? Or you just feel like asking the question again to derail this thread.

Your address may be associated with multiple transactions - incoming and outcoming - and all these transactions need to contain some information to be recognized by the network. The number of unspent transaction outputs depends on how many incoming transactions you have and how many of them have not been spent during other transactions. So, if you reuse an address, it may or may not contain additional UTXO since we take into account only unspent coins. For example, you receive 5 BTC in one transaction using your address X and later send it to address Y. As a result of such manipulations, you will have zero UTXOs associated with address X. If you use it again in another transaction to receive coins from address Z, your UTXO count will increase correspondingly.

For learning purposes I would even suggest to use Bitcoin Core Wallet cli. There you can see all available commands and a brief description of how they work. That way you can learn exactly how to spend from specific UTXOs, do the math, subtract fees, calculate fees, and never forget the CHANGE ADDRESS. Otherwise, the remaining Bitcoin you don't use in a specific transaction you build, will be sent to miners!

You can see it in your non custodial wallet. Turning on Coin Control feature and you will see more details.
List of useful Bitcoin block explorers (https://bitcointalk.org/index.php?topic=5197909.0)
If you use a non custodial wallet, you don't have to check your UTXO with block explorers because they will collect data from you when you visit their explorers, paste your Bitcoin address there.
If you don't want to expose your bitcoin wallet to Internet like a hot wallet, you can import its public address and get a watch-only wallet.

Creating a watch-only wallet with Electrum (https://bitcoinelectrum.com/creating-a-watch-only-wallet/)

UTXO, what does it mean?

It is Unspent outputs so if you have bitcoins in your wallet, you have UTXOs. Your wallet UTXO number will only become 0 if you have no bitcoin (no satoshi) in that wallet.
When you receive a first bitcoin transaction in your wallet, you have a first UTXO. Receive a second bitcoin transaction in your wallet, you have a second UTXO.

UTXO (Learnmeabitcoin) (https://learnmeabitcoin.com/technical/utxo)

Think of your address as a physical wallet you carry your cash in. UTXOs are the paper bills you have in your wallet. Each bill is one UTXO. If you sell something and receive BTC in address #1, that's one UTXO. You receive your salary to the same address, UTXO #2. Your friend losses a bet and sends the amount to address #1 - UTXO #3. Reusing addresses isn't recommended, but I am just making a point.

Let's not confused the OP by bringing wallets into the equation. I think OP is aware that transactions received in different addresses are separate UTXOs. His question was about how multiple transactions to the same address are to be called. As we have all said, it's the same thing - UTXOs.

You can't know the minimum spending balance per input ("input" types easier than "UTXO") without knowing the future fee, which you also can't know.

I always use coin control (in Electrum or Bitcoin Core). For each transaction I make, I manually pick the inputs that best fit the purpose based on transaction fee and privacy (linking inputs together). If fees are low, I consolidate (https://bitcointalk.org/index.php?topic=2848987.0) more and smaller inputs, if fees are high, I use as little inputs as possible.

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Maybe it's a good start to play around with fees on Testnet: get some coins (https://coinfaucet.eu/en/btc-testnet/), start Electrum with "--testnet" option, and create some transactions. Send some to yourself, learn how to use "send to many", send some back to the faucet, and see what happens to the fee and your Coins tab. On the Coins tab, manually select the inputs you want to use (the process is a bit different on the latest version of Electrum).