Layer 2

A secondary blockchain or network built on top of a base layer blockchain (Layer 1) that processes transactions off the primary chain and periodically settles them back to it, inheriting the security of the base layer while operating at higher throughput and lower cost. The Layer 2 concept emerged as the primary scaling approach for Ethereum after base layer scaling proved limited by the decentralization-security-scalability trilemma. L2s handle transaction execution separately, batching many transactions together and posting compressed summaries or cryptographic proofs to the L1, dramatically reducing per-transaction costs while maintaining L1-level security guarantees for withdrawals and final settlement. The dominant L2 architectures are optimistic rollups and ZK rollups, which differ in how they prove the validity of batched transactions to the base layer. Layer 2 also applies in other contexts including the Bitcoin Lightning Network, which is a payment channel L2 on Bitcoin. Example: Ethereum's Layer 2 ecosystem processed more daily transactions than Ethereum mainnet by 2024, with Arbitrum, Base, OP Mainnet, and zkSync Era collectively handling millions of daily transactions at costs of fractions of a cent while settling security to Ethereum. This inversion, where L2 activity exceeds L1 activity, validated the rollup-centric scaling roadmap that Vitalik Buterin and the Ethereum Foundation had articulated as Ethereum's long-term architecture. Why it matters for Web3: Layer 2 networks have been the primary mechanism through which Ethereum's user experience has improved from unusably expensive in 2021 to highly competitive with alternative L1s by 2024-2025. Without L2s, Ethereum's security model would come at a cost that made it impractical for most applications. With them, the ecosystem gets both the battle-tested security of the world's most decentralized smart contract platform and the throughput and cost structure needed for real-world applications.

Category: layer2 solutions

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