The Merge
Ethereum's 2022 transition from Proof of Work to Proof of Stake — one of crypto's largest engineering feats.
The Merge was Ethereum’s September 2022 switch from Proof of Work to Proof of Stake, executed live on a network securing hundreds of billions in value without downtime. It cut Ethereum’s energy consumption by roughly 99.95% overnight and replaced miners with validators staking ETH.
Its significance was both technical and narrative: it proved a major live blockchain could fundamentally rearchitect its security model, addressed the environmental critique aimed at crypto, and made ETH issuance far lower (occasionally deflationary via fee burning). It also sharpened the philosophical split with Bitcoin, which deliberately retains Proof of Work. The Merge is a reference point for what coordinated protocol upgrades can achieve.