<p>Yes, the question is answerable, although it might be hard to get the data to answer it (you would need blockchains from a few very long-running, well-connected nodes that contained both the main chain and orphan chains).</p>

<p>I don't know the answer. As ThePiachu says, the longest orphan chain was 53 blocks, but I don't think any confirmed-on-one-chain transactions ended up unconfirmed on the other chain-- I don't think there were any double-spends across those two chains.</p>

CC BY-SA 3.0
2012-06-27T15:26:26.520Z
2012-06-27T15:26:26.520Z
gavinandresen
<p>The longest orphaned fork was created due the <a href="https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2010-5139" rel="nofollow noreferrer">"value overflow" bug</a> occurrence, ranging from block 74638 to 74691 (so 53 blocks). Such a situation is unlikely to ever repeat though.</p>

<p>Other than that, as far as I remember 4 blocks were overwritten by some strange behaving miner (<a href="https://bitcoin.stackexchange.com/questions/3332/what-can-be-done-about-the-no-transaction-block-relayer-currently-71-123-170-15">related question</a>), but I might be mistaken.</p>

<p>In general, 6 confirmations is enough in most cases to prevent any double-spend attempts, and 120 confirmations is enough to give the developers time to release a fix for some major bug that might occur before the coin creation transactions are mixed in with everything else, creating a big mess.</p>

CC BY-SA 3.0
2012-06-27T02:23:27.043Z
2012-06-27T02:23:27.043Z
2017-04-13T12:47:33.583Z
ThePiachu
<p>I believe my two title questions are the same (are they?):</p>

<p>Heretofore, what is the longest chain of orphan blocks (of N blocks), such that if someone didn't wait for N+1 confirmations, they may have assumed transactions to be completed when they were not.</p>

<p>For example, on the wiki's blockchain article, it shows orphan chains of two blocks (N=2). In this case, 3 confirmations would have sufficed to confirm transaction with absolute accuracy. <a href="https://en.bitcoin.it/wiki/File:Blockchain.png">https://en.bitcoin.it/wiki/File:Blockchain.png</a></p>

<p>I ask because it seems 120 confirmations is the gold standard, if you will, as generated bitcoins take that long to confirm. Most other transactions are considered irrevocable at 6 blocks, but what has been the minimum, thus far? </p>

<p>PS. Is this question even answerable!?</p>

CC BY-SA 3.0
2012-06-27T05:20:49.137Z
possible duplicate of [What is the longest blockchain fork that has been orphaned to date?](http://bitcoin.stackexchange.com/questions/3343/what-is-the-longest-blockchain-fork-that-has-been-orphaned-to-date)
Thilo
<transactions><blockchain><confirmations><stale-block>
What's the longest chain of orphan blocks? (How many confirmations have been necessary?)
Streblo
# What's the longest chain of orphan blocks? (How many confirmations have been necessary?)

(Asked by: username_0 on 2012-06-27)

I believe my two title questions are the same (are they?):

Heretofore, what is the longest chain of orphan blocks (of N blocks), such that if someone didn't wait for N+1 confirmations, they may have assumed transactions to be completed when they were not.

For example, on the wiki's blockchain article, it shows orphan chains of two blocks (N=2). In this case, 3 confirmations would have sufficed to confirm transaction with absolute accuracy. <https://en.bitcoin.it/wiki/File:Blockchain.png>

I ask because it seems 120 confirmations is the gold standard, if you will, as generated bitcoins take that long to confirm. Most other transactions are considered irrevocable at 6 blocks, but what has been the minimum, thus far?

PS. Is this question even answerable!?

**Tags:** transactions, blockchain, confirmations, stale-block

> **Comments:**
> **username_1**: possible duplicate of [What is the longest blockchain fork that has been orphaned to date?](http://bitcoin.stackexchange.com/questions/3343/what-is-the-longest-blockchain-fork-that-has-been-orphaned-to-date)  

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## 2 answers

### Answer by username_3 on 2012-06-27. Score: 6 | Accepted answer

The longest orphaned fork was created due the ["value overflow" bug](https://en.bitcoin.it/wiki/Common_Vulnerabilities_and_Exposures#CVE-2010-5139) occurrence, ranging from block 74638 to 74691 (so 53 blocks). Such a situation is unlikely to ever repeat though.

Other than that, as far as I remember 4 blocks were overwritten by some strange behaving miner ([related question](https://bitcoin.stackexchange.com/questions/3332/what-can-be-done-about-the-no-transaction-block-relayer-currently-71-123-170-15)), but I might be mistaken.

In general, 6 confirmations is enough in most cases to prevent any double-spend attempts, and 120 confirmations is enough to give the developers time to release a fix for some major bug that might occur before the coin creation transactions are mixed in with everything else, creating a big mess.


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### Answer by username_2 on 2012-06-27. Score: 3

Yes, the question is answerable, although it might be hard to get the data to answer it (you would need blockchains from a few very long-running, well-connected nodes that contained both the main chain and orphan chains).

I don't know the answer. As username_3 says, the longest orphan chain was 53 blocks, but I don't think any confirmed-on-one-chain transactions ended up unconfirmed on the other chain-- I don't think there were any double-spends across those two chains.


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