Layer 1
The base blockchain — the foundational network responsible for consensus, security, and final settlement.
A Layer 1 (L1) is the base protocol blockchain: Ethereum, Bitcoin, Solana, Avalanche, BNB Chain. It is responsible for consensus (agreeing on the valid state of the chain), security, and final settlement of all transactions. Everything built on top inherits the L1's security guarantees.
L1s are constrained by the blockchain trilemma: maximising any two of security, scalability, and decentralisation comes at the expense of the third. Bitcoin prioritises security and decentralisation at the cost of throughput (~7 TPS). Solana prioritises throughput and speed, accepting more centralisation.
Ethereum's long-term roadmap (The Surge, The Verge, The Purge, The Splurge) aims to dramatically increase throughput via rollups and data shards while maintaining decentralisation and security.