Ethereum (ETH) is a blockchain platform that lets developers build and run applications without a central operator. Proposed by Vitalik Buterin and launched in 2015, it introduced smart contracts, which are programs that run automatically when set conditions are met. This is what powers decentralised finance (DeFi), NFTs, stablecoins and thousands of other applications. ETH is the network's native currency, used to pay transaction fees and to stake. Since the Merge in September 2022, Ethereum has run on proof of stake, where validators lock up ETH to secure the network, which cut its energy use by more than 99%. Ethereum is one of the largest crypto assets by market value and the base for many other tokens.