Mainnet genesis bloc (see https://etherscan.io/block/0) has 0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa as extraData value. It doesn't seem to convert to ascii and, as this field is free and can have any content, I wondered what does this value mean.

Anything geeky? Reference to a newspaper like in Bitcoin genesis?

1 Answer 1


From the Ethereum Blog post Final Steps

  • Block #1028201 is formed on the Ethereum tesnet, and is given a hash.
  • The hash is used by users around the world as a unique parameter to the Genesis block generation script

There's a repo for the script used to generate the genesis block https://github.com/ethereum/genesis_block_generator. From the README

Genesis block generator

Run as follows:

$ python mk_genesis_block.py --extradata <hash_from_#1028201> > genesis.json
  • What testnet was it and can we look at this block today? Jun 16, 2019 at 7:03
  • It was the Olympic test network. See ethereum.stackexchange.com/questions/10311/… for the history of test networks. It is no longer supported.
    – Ismael
    Jun 16, 2019 at 18:31
  • So this dada does not provide anything now that Olympic is off? We can't even run the scripts then? Jun 16, 2019 at 20:15
  • I think I do not understand your question. Only the hash is used as genesis block's extradata field so you do not need any other data from Olympic. The use of the hash from Olympic testnet was to make it fair for everyone to start mining on mainnet.
    – Ismael
    Jun 17, 2019 at 2:16
  • yes I get it, I meant that once the network was started and especially now that Olympic no longer exists, this data is mandatory in the genesis but useless. Jun 17, 2019 at 6:31

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