In September 2022, Ethereum made the transition from a power-hungry, proof-of-workproof-of-work system to an environmentally friendly proof-of-stakeproof-of-stake system. This switch is known as the "merge.” Here’s what you need to know.

What is the merge?

The merge changes the way that Ethereum transactions are validated. Previously, Ethereum worked like Bitcoin: transactions were mined by a decentralized network of computers, which raced to solve mathematical puzzles and were rewarded with new coins for doing so.

This "proof-of-work" consensus mechanism, which requires computers to agree on which transactions will be added to a new block, is very energy-intensive.

With the merge, Ethereum has transitioned to a consensus mechanism called proof-of-stake, which uses far less power and should make the network about 99% more energy-efficient, according to figures from the Ethereum Foundation.

What is Proof of Stake? How it Differs From Proof of Work

Mining cryptocurrency such as Bitcoin is an energy-intensive business. But it doesn’t have to be. Bitcoin, and other cryptocurrencies such as Dogecoin and Litecoin, secure their networks using the proof-of-work (PoW) consensus mechanism. An alternative consensus mechanism used by cryptocurrencies such as Ethereum is called proof-of-stake (PoS), which radically reduces the blockchain’s carbon footprint. In this article we’ll explore what consensus mechanisms are, and how proof-of-stake differs fr...

Under proof of stake, transactions are confirmed by addresses that have staked—pledged to a smart contractsmart contract—lots of ETH. Those who have staked more ETH earn proportionately higher rewards. While proof of stake conceptually makes the rich richer, it doesn’t boil the oceans, either.

The Ethereum community has been working on the transition to proof of stake ever since the blockchainblockchain launched in 2015.

The merge is one of a set of upgrades that should also make Ethereum faster and cheaper to use. Right now, Ethereum is beleaguered by slow transaction times and high costs. At peak congestion times, a simple swap on Uniswap for tokenstokens worth $1 could cost you over $50 in transaction fees.

Pre-merge, Ethereum could process 15 transactions per second. After the merge, it's 30 per second. Eventually, the post-merge protocol will supposedly support 100,000 transacations per second.

The merge itself won’t resolve high gas prices, however—it just sets the stage for a set of upgrades that will eventually cut costs. These upgrades used to be known as Ethereum 2.0, but that terminology was scrapped in early 2022.

What happened in the merge?

In December 2020, Ethereum launched the "beacon chain," a proof-of-stake chain that ran in parallel with the main Ethereum blockchain. The beacon chain was neutered; while users could stake ETH on it, the main functions of Ethereum weren't enabled.

The merge switched the mainnet version of Ethereum—the part that supports transactions and smart contracts—to be part of the beacon chain. Following the merge, the proof-of-work part of Ethereum will fall away, and mining will be gone forever.

Ethereum Successfully Executes Highly-Anticipated Merge Event, Ushering in Proof-of-Stake Era

At long last, the Ethereum merge has arrived.  At 2:45 am EST, the Ethereum network successfully began its transition—with no hiccups—from proof of work to proof of stake, a historic feat anticipated by the crypto community for over five years.  The upgrade has forever changed both how ETH is created and how transactions on the Ethereum network are validated. Up until the moment of the merge, ETH was generated by “mining,” an energy-intensive process by which individuals directed huge amounts of...

Post-merge, you’ll eventually be able to run smart contracts on mainnet Ethereum using proof of stake rather than proof of work. You’ll also be able to withdraw any ETH you’ve staked on Ethereum 2.0. You won’t be able to do this right after the merge, however. You’ll have to wait for yet another post-merge upgrade, which the Ethereum Foundation—the organization that oversees the development of the Ethereum blockchain—expects will happen “very soon” after the merge.

Specifically, withdrawals opened up once the Shanghai upgrade was executed in April 2023. Ethereum developer Marius van der Wijden is confident that Shanghai will be implemented in 2023.

When did the merge happen?

The merge took place on September 15, 2022, at 2:45 am EST. The event was triggered by Ethereum's mainnet hitting "terminal total difficulty," a predetermined point at which ETH mining became effectively impossible, with the network automatically switching over to the proof-of-stake consensus mechanism.

The merge itself took around 12 minutes to come into effect, with the success of the event signaled by the network successfully proposing and approving new blocks of transactions under the proof-of-stake consensus mechanism. The Ethereum network missed just one block during the transition and, after 12 minutes and 48 seconds, successfully reached finality.

During the merge, crypto exchanges paused trading for ETH and Ethereum-related tokens as a precautionary measure.

Do you need to do anything?

Probably not. The merge doesn't change anything about the history of Ethereum. You’ll still be able to head to block explorers like Etherscan to get a complete record of the Ethereum blockchain.

Of course, if you’re an Ethereum miner, you're now out of a job—you’ll have to mine somewhere else. Large-scale mining companies have been forced to rethink their business models, while many miners are expected to pivot to other proof-of-work blockchains. Some of these, such as Ethereum Classic and ETHPoW, are hard forkshard forks of the Ethereum blockchain.

 Ethereum 2.0

What the Ethereum Merge Means for Ordinary Users—And What It Doesn’t

The Ethereum merge is here. The long-awaited upgrade to the second biggest cryptocurrency by market cap is expected to take place tonight, based on current estimates.  So, what does that mean for you, the ordinary user or investor? Whether you’re holding your life savings in the asset or just 0.01 ETH, the network’s move from a proof-of-work blockchain to a proof-of-stake one will make things different. But what exactly?  For some time, there have been rumors swirling around that this upgrade wi...

One other thing: following the merge, the issuance of new Ethereum will reduce by about 90%. Ethereum’s issuance could even become deflationary if a lot of people use it.

What comes next?

Now that the merge has taken place, subsequent upgrades will increase the capacity and speed of the network by introducing “shard chains.” These will expand the network to 64 blockchains. The merge needs to happen first because these shard chains rely on staking.

The Ethereum Foundation noted that the need for scaling through shard chains has been offset somewhat by layer-2 scaling solutions, like Optimism and Arbitrum.

Layer-2 scaling solutions temporarily transition ETH and ERC-20 tokens to another blockchain, which completes computational busywork for a fraction of the cost and at a far lower price.

Eventually, shards will likely coexist with layer-2 technologies. The Ethereum Foundation says that the need for “multiple rounds of shard chains” will be metered by the Ethereum community, but that it could provide “endless scalability.”

Editor's note: This article was first published on April 13, 2022, and last updated on September 4, 2023.

Cheat Sheet

• With the merge, Ethereum has transitioned to a consensus mechanism called proof-of-stake, which uses far less power and should make the network about 99% more energy-efficient, according to figures from the Ethereum Foundation.
• If you’re an Ethereum miner, you’re out of a job after the merge.
• After the merge, subsequent upgrades will increase the capacity and speed of the network by introducing “shard chains.”

Up Next: The Shanghai Upgrade