Do you know if it is possible for ethereum forks to increase the 15s block time to for instance 1 min block time or 2 minutes block time?

Moreover I noticied that when we start new blockchain the miner can find blocks much quicker than 15s, so I assume it is linked to the difficulty in genesis.json. How much time should it take for a new blockchain to reach its actual block time? For instance in Bitcoin difficulty is adjusted every two weeks. Is there another field than difficulty we can fill in genesis.json to influence block time? Is the difficulty in genesis.json just used as a starting point or is it used for the whole blockchain life?

Is the 15s blocktime set somewhere in the source code as a parameter and is it possible to set it to 1min or 2 mins? Do you see unexpected possible problems for an ethereum fork with block time of 1 min or 2 mins?

Thank you very much!!!

1 Answer 1


The block time is basically a factor of the following things:

  1. Block difficulty. Decides how difficult it is to mine a block (solve the PoW puzzle)

  2. Network's hashing power

Balancing these two decides the block time. If the block time is longer than the target (probably because hashing power has decreased), difficulty is automatically decreased. And vice versa.

So, to get your desired block time in your own blockchain, adjust the initial difficulty. The difficulty will then start adjusting based on the requirements (the target block time is probably a variable somewhere).

  • Thank you! But given the fact that the hash power is variable how can the block time be stable (average 15s) ? It means the ethereum network constantly adapts difficulty to hash power? If so, how since difficulty is set in genesis.json, does it mean genesis.json is constantly changed? Thanks again
    – Kevin Wad
    Feb 8, 2022 at 7:16
  • The value in genesis is simply an initial value. It gets adjusted automatically, but the value in the genesis doesn't change. The current value is stored elsewhere Feb 8, 2022 at 7:16

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