Ethereum
Programmable blockchain for smart contracts and applications.
Ethereum is a decentralized blockchain platform designed to run smart contracts and applications. Its native asset, ETH, pays transaction fees and supports proof-of-stake security. Independent nodes verify blocks and execute the same contract instructions, creating a shared programmable state without one company controlling the ledger.
The Ethereum Virtual Machine executes contract bytecode deterministically. Developers commonly write contracts in Solidity, deploy them to an address, and connect them to web or mobile interfaces. Tokens, decentralized exchanges, lending markets, stablecoins, NFTs, identity tools, and DAOs use these contracts to coordinate assets and rules.
Ethereum matters because it introduced a widely adopted general-purpose blockchain environment. Open standards such as ERC-20 and ERC-721 allow assets to work across wallets and applications. Composability lets one protocol call another within the same transaction. A large developer ecosystem provides tooling, audits, infrastructure, and educational resources.
Ethereum changed from proof of work to proof of stake in the 2022 Merge. Validators deposit ETH, propose blocks, and attest to canonical history. Protocol penalties encourage correct operation, while slashing punishes certain conflicting behavior. Consensus security still depends on stake distribution, client diversity, operator practices, and social coordination around upgrades.
Base-layer block space is limited and can become expensive during high demand. Rollups batch transactions and use Ethereum for data and settlement, offering cheaper execution with additional contracts, sequencers, and bridge assumptions. Sidechains and alternative networks may be EVM-compatible without inheriting Ethereum security. The same address format or programming language does not make networks equivalent.
Users need ETH for gas and should verify the network, contract address, approvals, and transaction details before signing. Developers must plan for reorgs, node failures, contract upgrades, monitoring, and irreversible state changes. Public transactions provide auditability but limited privacy. Ethereum supports open, programmable infrastructure, yet smart contract bugs, scams, admin keys, oracle failures, and user mistakes remain outside what consensus alone can prevent.
Running a node gives users stronger independent verification, but requires storage, bandwidth, maintenance, and correct software. Most applications instead use RPC providers, creating availability and data-trust dependencies that teams should monitor.
Client diversity and geographically distributed validators help Ethereum continue operating when one implementation, hosting provider, or region experiences a serious failure.
Frequently asked questions
- Ethereum nodes run the Ethereum Virtual Machine, which executes deployed smart contract bytecode deterministically. Developers write applications that manage tokens, permissions, and shared state, while users call them through transactions. Gas meters resource use and prevents unlimited computation. Contracts are transparent and composable, but bugs and privileged upgrade controls can still place user assets at risk.
- The Merge, completed in September 2022, replaced proof-of-work block production with proof-of-stake consensus while preserving the existing execution state. Validators now stake ETH and attest to blocks instead of miners competing with computation. The change greatly reduced direct network energy use and altered issuance. It did not immediately lower transaction fees or increase base-layer capacity.
- Ethereum primarily scales activity through Layer 2 rollups that execute transactions separately and publish data plus state commitments or proofs to Ethereum. Optimistic rollups use challenge periods, while validity rollups submit cryptographic proofs. Fees, finality, sequencers, bridges, data availability, and upgrade controls differ. Users should evaluate the complete rollup rather than assume every Layer 2 has identical security.