<p>No. <strong>A zero-confirmation transaction is not useful for anything.</strong> Satoshi used PoW specifically, because he was trying to answer <em>how to trust a transaction</em>(double-spending problem).</p>

<p>Secondly, <strong>transaction replacement was introduced by Satoshi in the first release of the Bitcoin software</strong>, but was later removed due to denial-of-service problems.</p>

CC BY-SA 3.0
2018-02-18T06:11:05.800Z
Sources, please.
Lubo Kanev
CC BY-SA 3.0
2018-02-17T00:13:07.390Z
2018-02-17T00:20:32.783Z
2018-02-17T00:20:32.783Z
skang404
<p>RBF is optional and it can be seen if a particular transaction has RBF enabled or not. For transactions without RBF enabled, they are as 0-conf secure as they were previously.</p>

CC BY-SA 3.0
2018-02-18T06:11:39.993Z
Except when blocks are full.
Lubo Kanev
CC BY-SA 3.0
2018-02-18T07:07:17.457Z
@LuboKanev Whether or not blocks are full has not changed how secure 0-conf is or is not. It was always recommended to wait for six confirmations. Otherwise, you just accept that a transaction exists and suppose that it will be included in a block eventually.
Willtech
CC BY-SA 3.0
2018-02-18T08:53:58.050Z
Small merchants always used 0-conf so far. If blocks are not full, your transaction doesn't just get in eventually, it get's in in the very next block. When they are full it may never get in, or perhaps 6-conf can take days.
Lubo Kanev
CC BY-SA 3.0
2018-02-18T09:01:34.763Z
@LuboKanev True, except, there was never any guarantee the transaction would be in the next block, even if that was what always happened.
Willtech
CC BY-SA 3.0
2018-02-20T19:47:08.300Z
I agree. But that's why it's only used for small purchases.
Lubo Kanev
CC BY-SA 3.0
2018-02-17T01:56:52.830Z
2018-02-17T02:52:46.283Z
2018-02-17T02:52:46.283Z
Willtech
<p>RBF and full blocks make 0-conf useless, because it's easy to override. Wasn't it once useful? I've heard without those it's more secure than Visa in terms of double spending. </p>

CC BY-SA 3.0
2018-02-17T02:57:59.783Z
I don't know how one would measure "more secure than Visa".  Certainly there are no formal security guarantees for zero-conf transactions.  Someone might have gathered statistics on what fraction of transactions were actually double-spent, and compared it to Visa chargeback rates, but it's not clear that this is a valid comparison; for instance, lots of Bitcoin transactions involve people sending money to themselves.
Nate Eldredge
<blocksize><zero-confirmation><replace-by-fee><visa>
Wasn't 0-conf more secure than Visa, before blocks got full and RBF was added?
Lubo Kanev
# Wasn't 0-conf more secure than Visa, before blocks got full and RBF was added?

(Asked by: username_0 on 2018-02-16)

RBF and full blocks make 0-conf useless, because it's easy to override. Wasn't it once useful? I've heard without those it's more secure than Visa in terms of double spending.

**Tags:** blocksize, zero-confirmation, replace-by-fee, visa

> **Comments:**
> **username_1**: I don't know how one would measure "more secure than Visa".  Certainly there are no formal security guarantees for zero-conf transactions.  Someone might have gathered statistics on what fraction of transactions were actually double-spent, and compared it to Visa chargeback rates, but it's not clear that this is a valid comparison; for instance, lots of Bitcoin transactions involve people sending money to themselves.  

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## 2 answers

### Answer by username_2 on 2018-02-17. Score: 2

No. **A zero-confirmation transaction is not useful for anything.** Satoshi used PoW specifically, because he was trying to answer *how to trust a transaction*(double-spending problem).

Secondly, **transaction replacement was introduced by Satoshi in the first release of the Bitcoin software**, but was later removed due to denial-of-service problems.

> **Comments:**
> **username_0**: Sources, please.  

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### Answer by username_3 on 2018-02-17. Score: 2

RBF is optional and it can be seen if a particular transaction has RBF enabled or not. For transactions without RBF enabled, they are as 0-conf secure as they were previously.

> **Comments:**
> **username_0**: Except when blocks are full.  
> **username_3**: @username_0 Whether or not blocks are full has not changed how secure 0-conf is or is not. It was always recommended to wait for six confirmations. Otherwise, you just accept that a transaction exists and suppose that it will be included in a block eventually.  
> **username_0**: Small merchants always used 0-conf so far. If blocks are not full, your transaction doesn't just get in eventually, it get's in in the very next block. When they are full it may never get in, or perhaps 6-conf can take days.  
> **username_3**: @username_0 True, except, there was never any guarantee the transaction would be in the next block, even if that was what always happened.  
> **username_0**: I agree. But that's why it's only used for small purchases.  

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