The merge

What is the merge?

It's important to remember that initially, the Beacon Chain shipped separately from Mainnet - the chain we use today. Ethereum Mainnet continues to be secured by proof-of-work, even while the Beacon Chain runs in parallel using proof-of-stake. The merge is when these two systems finally come together.

Imagine Ethereum is a space ship that isn’t quite ready for an interstellar voyage. With the Beacon Chain the community has built a new engine and a hardened hull. When it’s time, the current ship will dock with this new system, merging into one ship, ready to put in some serious lightyears and take on the universe.

Merging with Mainnet

When ready, Ethereum Mainnet will "merge" with the Beacon Chain, becoming its own shard which uses proof-of-stake instead of proof-of-work.

Mainnet will bring the ability to run smart contracts into the proof-of-stake system, plus the full history and current state of Ethereum, to ensure that the transition is smooth for all ETH holders and users.

After the merge

This will signal the end of proof-of-work for Ethereum and start the era of a more sustainable, eco-friendly Ethereum. At this point Ethereum will be one step closer to achieving the full scale, security and sustainability outlined in its Eth2 vision.

It is important to note that an implementation goal of the merge is simplicity in order to expedite the transition from proof-of-work to proof-of-stake. Developers are focusing their efforts on this transition, and minimizing additional features that could delay this goal.

This means a few features, such as the ability to withdraw staked ETH, will have to wait a little longer after the merge is complete. Plans include a post-merge "cleanup" upgrade to address these features, which is expected to happen very soon after the merge is completed.

Relationship between upgrades

The Eth2 upgrades are all somewhat interrelated. So let’s recap how the merge relates to the other upgrades.

The merge and the Beacon Chain

Once the merge happens, stakers will be assigned to validate the Ethereum Mainnet. Mining will no longer be required so miners will likely invest their earnings into staking in the new proof-of-stake system.

The merge and the post-merge cleanup

Immediately after the merge, some features such as withdrawing staked ETH, will not yet be supported. These are planned for a separate upgrade to follow shortly after the merge.

Stay up-to-date with the EF Research and Development Blog. For those curious, learn more about What Happens After the Merge, presented by Vitalik at the April 2021 ETHGlobal event.

The merge and shard chains

Originally, the plan was to work on shard chains before the merge – to address scalability. However, with the boom of layer 2 scaling solutions, the priority has shifted to swapping proof-of-work to proof-of-stake via the merge.

This will be an ongoing assessment from the community as to the need for potentially multiple rounds of shard chains to allow for endless scalability.