The base blockchain itself (Bitcoin, Ethereum, Solana) — the foundation that other layers and applications build upon.
A Layer 1 (L1) is the base blockchain that operates independently with its own consensus mechanism, validator set, and native token. L1s are the foundation of the crypto ecosystem — everything else (L2s, dApps, tokens) is built on top of them. Major L1s include Bitcoin (the original, focused on sound money), Ethereum (smart contracts and DeFi), Solana (high-speed, low-cost), BNB Chain (Binance ecosystem), Cardano (peer-reviewed development), and Avalanche (subnet architecture). Each L1 makes different tradeoffs in the blockchain trilemma of security, decentralization, and scalability. L1s compete for developers, users, and capital — the 'L1 wars' drove much of the 2021 bull market narrative. Today, the trend is toward a multi-chain future where multiple L1s coexist, connected by bridges and interoperability protocols.
Layer 1 refers to the base blockchain that provides its own security, consensus, and transaction settlement — Bitcoin, Ethereum, Solana, Avalanche, and Cardano are all Layer 1s. Each L1 makes fundamental design trade-offs that define its character: Bitcoin optimizes for security and decentralization with 10-minute blocks; Solana optimizes for speed with 400ms blocks but higher hardware requirements; Ethereum pursues a rollup-centric roadmap delegating execution to L2s. The 'blockchain trilemma' describes the challenge of simultaneously achieving decentralization, security, and scalability — L1s must choose which properties to prioritize. The L1 landscape has evolved from 'Ethereum killer' narratives to a multi-chain reality where different L1s serve different use cases. Some L1s focus on specific niches: Sei for trading, Celestia for data availability, Filecoin for storage, and Injective for financial applications.
Ethereum is a Layer 1 blockchain that processes ~1M transactions daily and secures $50B+ in DeFi TVL — while Layer 2s like Arbitrum and Optimism build on top of it for cheaper, faster transactions.
This is debated. Multi-chain advocates argue different L1s serve different needs (speed vs decentralization vs privacy). L1 maximalists argue most value will concentrate on one or two dominant chains. In practice, the market supports multiple L1s, but network effects tend to concentrate activity — Ethereum and Solana currently dominate DeFi and consumer apps respectively.