https://ethereum.org/en/upgrades/merge/
~Q3/Q4 2022
The Merge is the most significant upgrade in the history of Ethereum. Extensive testing and bug bounties were undertaken to ensure a safe transition to proof-of-stake.
This process is in its final stages, with plans to undergo The Merge on a few public testnets before finally moving forward with Mainnet. If you're excited about The Merge, follow the EF Blog or the client communication channels for the latest official word on When Merge?
The Merge represents the joining of the existing execution layer of Ethereum (the Mainnet we use today) with its new proof-of-stake consensus layer, the Beacon Chain. It eliminates the need for energy-intensive mining and instead secures the network using staked ETH. A truly exciting step in realizing the Ethereum vision – more scalability, security, and sustainability.
It's important to remember that initially, the Beacon Chain shipped separately from Mainnet. Ethereum Mainnet - with all it's accounts, balances, smart contracts, and blockchain state - continues to be secured by proof-of-work, even while the Beacon Chain runs in parallel using proof-of-stake. The approaching Merge is when these two systems finally come together, and proof-of-work is replaced permanently by proof-of-stake.
Let's consider an analogy. Imagine Ethereum is a spaceship that isn't quite ready for an interstellar voyage. With the Beacon Chain, the community has built a new engine and a hardened hull. After significant testing, it's almost time to hot-swap the new engine for the old mid-flight. This will merge the new, more efficient engine into the existing ship, ready to put in some serious lightyears and take on the universe.
Since genesis, proof-of-work has secured Mainnet. This is the Ethereum blockchain we're all used to—it contains every transaction, smart contract, and balance since it began in July 2015.
Throughout Ethereum's history, developers have been hard at work preparing for an eventual transition away from proof-of-work to proof-of-stake. On December 1, 2020, the Beacon Chain was created, which has since existed as a separate blockchain to Mainnet, running in parallel.
The Beacon Chain has not been processing Mainnet transactions. Instead, it has been reaching consensus on its own state by agreeing on active validators and their account balances. After extensive testing, the Beacon Chain's time to reach consensus on more is rapidly approaching. After The Merge, the Beacon Chain will be the consensus engine for all network data, including execution layer transactions and account balances.
The Merge represents the official switch to using the Beacon Chain as the engine of block production. Mining will no longer be the means of producing valid blocks. Instead, the proof-of-stake validators assume this role and will be responsible for processing the validity of all transactions and proposing blocks.
No history is lost. As Mainnet gets merged with the Beacon Chain, it will also merge the entire transactional history of Ethereum. You don't need to do anything. Your funds are safe.
This transition to proof-of-stake will come with some changes to the way ether is supplied. Learn more about ether issuance before and after The Merge.
The Merge is one of the most significant and anticipated upgrades in the history of Ethereum, and although in the long-term its impact will be felt by everyone, in the near-term some folks will need to take action to be fully prepared.
You do not need to do anything to protect your funds entering The Merge.
This bears repeating: As a user or holder of ETH or any other digital asset on Ethereum, as well as non-node-operating stakers, you do not need to do anything with your funds or wallet before The Merge.
Despite swapping out proof-of-work, the entire history of Ethereum since genesis remains intact and unaltered after the transition to proof-of-stake. Any funds held in your wallet before The Merge will still be accessible after The Merge. No action is required to upgrade on your part.