The “Merge”

The Merge was the joining of the original version of the Ethereum blockchain (which was initially launched in 2015 and used a proof-of-work consensus mechanism) with its new proof-of-stake consensus layer.  The Merge was executed on September 15, 2022. The Merge represented the official switch to using proof-of-stake as the mechanism for block production on the Ethereum network. Despite the change in the consensus mechanism, the entire transactional history of Ethereum remained unchanged.