Ethereum’s New Testnet Holesky Fails While Launching

The misplacement of parameters causes an error to load the genesis block of the to-be largest Ethereum testnet.

Last updated: July 7, 2025 3:24 PM

Published September 16, 2023 11:47 AM

Last updated: July 7, 2025 3:24 PM

Published September 16, 2023 11:47 AM

The newly introduced Ethereum test network, Holesky has failed to launch due to a misconfiguration in genesis files.

To celebrate the first anniversary of Merge upgrade, the Holesky testnet was set to go live on 15th September. However, the testing network has not even reached the genesis block.

Holesky Testnet Explorer Source: Beaconcha.in

Ethereum researcher proto.eth outlined the error that a developer misplaced extra-data in the genesis files which resulted in the testnet failing. He also noted that some other fork parameters are also mismatching.

Someone put 0x686f77206d7563682069732074686520666973683f ("how much is the fish?") as extra-data in the EL Holesky genesis.json, and not in the CL genesis.ssz

Misconfiguration, network failed to launch.

Also, some other fork params in releases are rumored to mismatch too.

Need…
— proto.eth (@protolambda) September 15, 2023

Holesky was to become the biggest Ethereum testing network while replacing the popular Goerli testnet. With 1.4 million validators, it will become twice the size of Ethereum mainnet which currently has 790k validators.

A post from researcher and developer firm Nethermind confirmed that the Ethereum Foundation and clients team has decided to relaunch Holesky after a week.