Ethereum (ETH) is a decentralized, open-source blockchain platform that lets developers build and run smart contracts and decentralized applications (dApps). Often called "the world computer," Ethereum was first proposed in a 2013 white paper by Vitalik Buterin and launched in 2015. Unlike Bitcoin, which is limited to peer-to-peer payments, Ethereum was designed to let anyone build and deploy their own applications on a shared, permissionless network.
Ethereum's core innovation is the smart contract: a self-executing program with its terms written directly into code, running without a central server. This capability enabled decentralized finance (DeFi), non-fungible tokens (NFTs), and blockchain gaming to grow into major sectors built on top of Ethereum.
Ether (ETH) is Ethereum's native token, used to pay transaction costs called "gas," that fund smart contract execution and network security. In August 2021, the London upgrade introduced EIP-1559, which burns a portion of each transaction's gas fee, adding deflationary pressure to ETH's supply during periods of high network activity.
On September 15, 2022, Ethereum completed "The Merge," switching its consensus mechanism from energy-intensive Proof-of-Work (PoW) to Proof-of-Stake (PoS); the Ethereum Foundation estimated this cut network energy use by about 99.95%. A minority of miners forked the pre-Merge chain into EthereumPoW (ETHW) to keep using Proof-of-Work. ETH has no fixed maximum supply. As of late June 2026, circulating supply was about 120.7 million ETH, with a market cap of roughly $196 billion, ranking #2 by market capitalization according to CoinGecko and CoinMarketCap. As of early 2026, roughly 30% of circulating ETH was staked to help secure the network, according to CoinGecko.