<p>Anyone can fork Bitcoin, they don't even need to be a miner. The general steps are:</p>
<ul>
<li>First and foremost, you need to change some consensus rules. Without this step, you aren't actually creating a new cryptocurrency, because Bitcoin <em>is</em> the consensus rules.
<ul>
<li>Assuming you don't expect your fork to have more hashrate than Bitcoin when it launches, you need to make sure future Bitcoin blocks won't be valid on your fork, otherwise your fork's blocks will just get overwritten (i.e. a soft fork – see <a href="https://bitcoin.stackexchange.com/q/108155/121614">Does a hard fork need to include a soft fork as well?</a>). This also applies to other forks that you might accidentally be compatible with.</li>
<li>To allow people to transact on one chain without their transactions being replayed on the other, you need to implement some form of replay protection, for example by changing the sighash algorithm.</li>
<li>A commonly implemented consensus rule change in Bitcoin forks is changing to a more responsive difficulty adjustment algorithm and/or a one-time difficulty decrease at the fork height, otherwise you might have to wait a long time before even a single block is mined. If you make the difficulty low enough you can even mine on a CPU before it goes back up (you could also change the proof-of-work algorithm to an ASIC-resistant one).</li>
<li>Pick a specific block (preferably in the near future) where your fork will start.</li>
</ul>
</li>
<li>To launch a new peer-to-peer network you should also change the network magic number, or make any other invasive change to the peer-to-peer protocol that makes it incompatible with the Bitcoin network. You also want new DNS seeds.</li>
<li>Watch as your fork falls into irrelevance, assuming it ever had any relevance to begin with.</li>
</ul>

CC BY-SA 4.0
2024-05-31T03:19:02.967Z
2024-06-07T18:04:31.760Z
2024-06-07T18:04:31.760Z
Vojtěch Strnad
<p>I understand in the past the blockchain has been forked (I.e BCH, etc). Can this be done by a single miner? How exactly does this happen?</p>

<altcoin><blockchain-fork>
How can the Bitcoin blockchain be forked?
Jake Stanton
# How can the Bitcoin blockchain be forked?

(Asked by: username_0 on 2024-05-31)

I understand in the past the blockchain has been forked (I.e BCH, etc). Can this be done by a single miner? How exactly does this happen?

**Tags:** altcoin, blockchain-fork


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## 1 answers

### Answer by username_1 on 2024-05-31. Score: 6

Anyone can fork Bitcoin, they don't even need to be a miner. The general steps are:

* First and foremost, you need to change some consensus rules. Without this step, you aren't actually creating a new cryptocurrency, because Bitcoin *is* the consensus rules.
  + Assuming you don't expect your fork to have more hashrate than Bitcoin when it launches, you need to make sure future Bitcoin blocks won't be valid on your fork, otherwise your fork's blocks will just get overwritten (i.e. a soft fork – see [Does a hard fork need to include a soft fork as well?](https://bitcoin.stackexchange.com/q/108155/121614)). This also applies to other forks that you might accidentally be compatible with.
  + To allow people to transact on one chain without their transactions being replayed on the other, you need to implement some form of replay protection, for example by changing the sighash algorithm.
  + A commonly implemented consensus rule change in Bitcoin forks is changing to a more responsive difficulty adjustment algorithm and/or a one-time difficulty decrease at the fork height, otherwise you might have to wait a long time before even a single block is mined. If you make the difficulty low enough you can even mine on a CPU before it goes back up (you could also change the proof-of-work algorithm to an ASIC-resistant one).
  + Pick a specific block (preferably in the near future) where your fork will start.
* To launch a new peer-to-peer network you should also change the network magic number, or make any other invasive change to the peer-to-peer protocol that makes it incompatible with the Bitcoin network. You also want new DNS seeds.
* Watch as your fork falls into irrelevance, assuming it ever had any relevance to begin with.


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