Confused with wallet addresses

[Thomasio]

I have a question where I'm not even sure how to explain it.
Basically I keep reading suggestions that one should use a new address for every transaction and I'm wondering how I could do that.

I've never transferred any bitcoin from my wallet, I've just received into my wallet, from multiple sources and to multiple addresses because I gave the senders always newly generated addresses to send to.

Now suppose I would want to send some of it somewhere, an exchange to sell or trade, or a merchant to buy something.

I suppose if the transaction is larger than the amount present on any single address, the wallet manages automatically sending from as many addresses as are required to fill the amount to transfer.
But what happens if the transaction is smaller than the amount present on an address?
Wouldn't that mean that upon next transfer I'll be sending from the same address again and isn't that exactly what one shouldn't do?

[1715113502]

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[RabbiTANK]

What? You don't have to generate a new address everytime you wan to receive funds in your wallet, your once generated address is enough, you make it sound like wallet address expires once you used them for a single transaction.

The transaction won't be successful if the available fund in your wallet is lower than the exact amount you trying to send out to others, bitcoin wallet works just like a bank account, you can only send out the exact amount you have in your wallet, not higher but exact or lower

[Yogee]

Basically I keep reading suggestions that one should use a new address for every transaction and I'm wondering how I could do that.

What wallet are you using? You can generate new address if you're using non-custodial wallet as far as I'm aware.
A new one called a "change address" is also generated whenever you send btc. It's where "left overs" are sent to.

I've never transferred any bitcoin from my wallet, I've just received into my wallet, from multiple sources and to multiple addresses because I gave the senders always newly generated addresses to send to.

Huh? I thought you didn't know how to generate new addresses?

I suppose if the transaction is larger than the amount present on any single address, the wallet manages automatically sending from as many addresses as are required to fill the amount to transfer.

Correct.

But what happens if the transaction is smaller than the amount present on an address? Wouldn't that mean that upon next transfer I'll be sending from the same address again and isn't that exactly what one shouldn't do?

The change will be sent to a change address as mentioned above. It's an address you also own and have access to. The funds will come from there he next time you send.

......

Some wallets like electrum have a feature called coin control. It basically allows you to choose which address to send from.

[OcTradism]

Where you store your bitcoin? In wallet or in exchange wallet?

You should be your own bank with non-custodial wallets: Bitcoin Core or Electrum wallet. Bitcoin Core full node requires huge space in disk, if you don't have much but want to use Bitcoin Core, use prune node. Electrum has app for Android (get link to download the app from the link, don't search Electrum on Google Play)

You can check and turn on change address in your wallet, Replace by fee.

In Electrum, if you want to send bitcoin from address A (in Address tab, choose Address A and right click to choose Spend from).
Click on Send tab to fill in the address of receiver.
Click on amount (can choose Max amount from address A or any amount you want to send)
Click on Pay: You will see the message box, see in Fee rate: default is ETA that is high fee usually. You could change it to mempool. The fee now is high so the lowest fee you can use fee for 10 MB from tip with the fee is 6 sat/byte.
If you accept that fee, enter password, click on Send: You will see details for the transaction (amount send, fee)
If you see things are ok, click on Broadcast, Finalize, and that amount will be sent.

But what happens if the transaction is smaller than the amount present on an address?

You can not send more than the amount you have.

But you can click on 2 or 3 or multiple address in one wallet to spend it. Right click > Spend from and do same steps.

[Thomasio]

Hmmmmmm ........ was I really so bad in explaining?
You seem not to understand what I mean.

Of course I know how to generate addresses and of course those are receiving addresses of my wallet.
Of course I cannot generate an address to send to, because that's the address I want to send to and that one the receiver has to generate.

I am aware of addresses where change goes into, but ....... that's where I'm not sure how to explain it.

Let's say I received 0.1BTC from somewhere into one of my addresses.
Now I spend 0.001BTC on something and my wallet sends it from that address.
That leaves 0.099BTC on that address, but that address has now been used as a sending address and the next time I spend 0.001BTC on something, my wallet would use the same sender address, because that's where the 0.099BTC are and that's (as far as I understood) is what one shouldn't do.

Or did I get that wrong?

[OcTradism]

Let's say I received 0.1btc from somewhere into one of my addresses.
Now I spend 0.001BTC on something and my wallet sends it from that address.
That leaves 0.099BTC on that address, but that address has now been used as a sending address and the next time I spend 0.001BTC on something, my wallet would use the same sender address, because that's where the 0.099BTC are and that's (as far as I understood) is what one shouldn't do.

It is about Change address I mentioned.

In Electrum:
Tools, Preferences, Transactions. You will see the Use change address. Choose this one if it has not yet been chosen in your wallet.
You will see 2 parts (in Green and Yellow colours) in the Address tab: Green is for initial receiving address, Yellow is for change address.

Change: The way bitcoin works unspent outputs have to be spent in their entirety. Excess amounts are sent back to a change address in your wallet. To confirm that this is the case right click on the transaction in question on the history tab and choose details. See if the unknown output in question is highlighted in green or yellow. Yellow refers to change addresses while green means receive address. Both change and receiving addresses are a part of your wallet meaning these coins were sent back to your wallet. You control this money and it is yours.

[Thomasio]

Hmmmmm, now for dummies, let me see if I got that right.

If I have 0.1BTC on an address and I spend 0.001 of it, the entire rest of 0.099BTC gets moved to a change address?
If yes, then that's the answer to my question and I'll be perfectly happy with it.

Just one follow up question: If I reinstall my PC and ...... um "forget" to save my wallet file, meaning I have to restore my wallet through "importprivkey", will I have to have all the private keys of all the change addresses or do all the change addresses use the same private key?

[Yogee]

Hmmmmm, now for dummies, let me see if I got that right.

If I have 0.1BTC on an address and I spend 0.001 of it, the entire rest of 0.099BTC gets moved to a change address?
If yes, then that's the answer to my question and I'll be perfectly happy with it.

Yes.

Like I said

But what happens if the transaction is smaller than the amount present on an address? Wouldn't that mean that upon next transfer I'll be sending from the same address again and isn't that exactly what one shouldn't do?

The change will be sent to a change address as mentioned above. It's an address you also own and have access to. The funds will come from there he next time you send.

[NeuroticFish]

Just one follow up question: If I reinstall my PC and ...... um "forget" to save my wallet file, meaning I have to restore my wallet through "importprivkey", will I have to have all the private keys of all the change addresses or do all the change addresses use the same private key?

Nope.
One private key is for one address. The change address will have a different private key.

That's why the actual wallet has to be backed up if you use Bitcoin Core for example.
If you use a HD wallet instead (like Electrum), then you'll have to keep safe a mnemonic seed (12-24 words) and all the addresses in the wallet (including the change addresses) can be re-created from that seed.

[Thomasio]

That's why the actual wallet has to be backed up if you use Bitcoin Core for example.
If you use a HD wallet instead (like Electrum), then you'll have to keep safe a mnemonic seed (12-24 words) and all the addresses in the wallet (including the change addresses) can be re-created from that seed.

I have both, Bitcoin Core as well as Electrum, because I have one on my PC and one on my mobile, but both using the same ...... ermmmm what would that be? ..... same wallet, same address, same private key, same seed ..... hope you know what I mean.
Makes me wonder how that seed could recreate addresses that weren't there at the time the seed was created.

[NeuroticFish]

I have both, Bitcoin Core as well as Electrum, because I have one on my PC and one on my mobile, but both using the same ...... ermmmm what would that be? ..... same wallet, same address, same private key, same seed ..... hope you know what I mean.
Makes me wonder how that seed could recreate addresses that weren't there at the time the seed was created.

Well, newer Bitcoin Core is also HD wallet (works internally with all addresses based on a seed) just doesn't "publish" it like Electrum.
(maybe this post could enlighten you: https://bitcointalk.org/index.php?topic=5215266.msg53539363#msg53539363)

However, it's possible to get the same into both, but what I wrote was the recommended way to backup both.
I am not sure what you have done to have same addresses in both and I would not make too many assumptions since I may go in a wrong direction.

The easiest to have "same in both" is to import one private key. But then one of the wallets (the second) will have only one address (ever), no change addresses and such.

[OcTradism]

Private key and mnemonic seed are different visual display for your bitcoin private key.

Private key is a long string of characters but mnemonic seeds are 12 or 24 words but those words are to store your private key. They serve same purpose, store your private key.

Different BIP will create different mnemonic seed from same private key.
To import one private key from one wallet provider to another wallet provider, you need to have technical match from two wallets.

You can learn from https://iancoleman.io/bip39/

HD wallet: see the chapter 5 in Mastering bitcoin.

[odolvlobo]

That's why the actual wallet has to be backed up if you use Bitcoin Core for example.
If you use a HD wallet instead (like Electrum), then you'll have to keep safe a mnemonic seed (12-24 words) and all the addresses in the wallet (including the change addresses) can be re-created from that seed.

I have both, Bitcoin Core as well as Electrum, because I have one on my PC and one on my mobile, but both using the same ...... ermmmm what would that be? ..... same wallet, same address, same private key, same seed ..... hope you know what I mean.
Makes me wonder how that seed could recreate addresses that weren't there at the time the seed was created.

I would be surprised if your Bitcoin Core and Electrum wallets are using the same addresses and private keys. To be safe, you should back up your Bitcoin Core wallet (there is an option in the menu) and save the Electrum recovery phrase (aka seed or mnemonic). If you don't back up both of them, you could lose bitcoins.

Private key and mnemonic seed are different visual display for your bitcoin private key.
Private key is a long string of characters but mnemonic seeds are 12 or 24 words but those words are to store your private key. They serve same purpose, store your private key.
Different BIP will create different mnemonic seed from same private key.
To import one private key from one wallet provider to another wallet provider, you need to have technical match from two wallets.
You can learn from https://iancoleman.io/bip39/
HD wallet: see the chapter 5 in Mastering bitcoin.

Your explanation is completely wrong.

A mnemonic/seed/recovery phrase is not a private key. It doesn't store a private key. The seed is used by the wallet to generate all the addresses and private keys that the wallet will use. In other words, every time a wallet generates a new private key and address, it uses its mnemonic/seed/recovery phrase to generate it.

BIP stands for Bitcoin Improvement Protocol. BIP-32 is the system that wallets use to generate private keys from a mnemonic. A mnemonic is not created from a private key. That is exactly backwards..

[Thomasio]

Why shouldn't I have the same address in both, Bitcoin Core and Eletrum?
Both have the option to import private keys, so whenever I generate a receiving address with one wallet, I dump the private key from it and import that into the other wallet.
Since I've never spent any Bitcoin, I never had to deal with automatically generated change addresses.