Ethereum's First Mainnet Shadow Fork Goes Live as Move to PoS Continues

The shadow fork will stress test developers' assumptions on existing testnets and the mainnet.

AccessTimeIconApr 11, 2022 at 3:10 p.m. UTC
Updated May 11, 2023 at 3:43 p.m. UTC

Ethereum's first mainnet shadow fork went live today, as the developers of the world's second-largest cryptocurrency by market cap continue transitioning the backing network to a proof-of-stake (PoS) model.

The shadow fork is a way to "stress test our assumptions around syncing and state growth," tweeted Parithosh Jayanthi, an Ethereum Foundation developer, on April 10. He added that it will also provide "a way to check if our assumptions work on existing testnets and/or mainnet."

Ethereum has been working on a multi-stage shift to a PoS consensus algorithm that will replace the current proof-of-work (PoW) mechanism. In the PoS model, transactions will be validated by nodes run by “stakers” instead of “miners.” The switch is expected to significantly reduce the energy required for the network to run, a key point of contention for the Bitcoin network, which runs on PoW.

The shadow fork will share some of the data with the main Ethereum network, so some transactions could appear on both chains, Jayanthi cautioned. The shadow fork has already processed 1,166,016 transactions with an average block time of 14.8 seconds as of the time of writing, according to a block explorer page shared by the developer Marius Van Der Wijden.

The outcome of the shadow fork is key to determining the timing of the final merge, said Ethereum developer Tim Beiko, according to Galaxy Digital Research Associate Christine Kim.

'Historical event'

Earlier on Monday, Van Der Wijden, an Ethereum Foundation developer who came up with the shadow fork, according to Jayanthi, tweeted that the shadow fork is a "historical event." The foundation has previously tried shadow forks of the Görli testnet, a proof-of-authority blockchain used for testing decentralized applications.

In mid-March, another key milestone was reached with Kiln testnet merge, when a PoW execution layer merged with a PoS Beacon Chain. This was scheduled as the last merge testnet before the final move to PoS.

According to Jayanthi, the Kiln merge testnet was designed "to allow the community to practice running their nodes, deploying contracts, testing infrastructure, etc." The shadow fork goes a step further to stress test the network, he said.

Once today's shadow fork went live, the developer team noticed some issues with Ethereum-based software systems provider Nethermind and Hyperledger Besu, a Java-based open-source Ethereum client, Jayanthi tweeted on Monday.

The percentage of validators doing their job, also known as the participation rate in the network, dropped, but the network is still above the mining requirement for finality, according to Jayanthi.


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Eliza Gkritsi

Eliza Gkritsi is a CoinDesk contributor focused on the intersection of crypto and AI.