Layer 2 (L2) is a collective term for off-chain scaling solutions that inherit the security of a Layer 1 blockchain while processing transactions faster and cheaper. Major categories include Optimistic Rollups (Arbitrum, Optimism) and ZK Rollups (StarkNet, zkSync).
2019
Lightning Network and state channels emerge as early L2 solutions
2021
Arbitrum and Optimism launch — Ethereum L2 ecosystem begins
2022
Total L2 TVL exceeds $5B
2023
Coinbase launches Base L2; ZK rollups mature with mainnet launches
Cheap and fast Ethereum transactions, DeFi, gaming, NFTs at scale
💡 Did You Know
At peak congestion, Ethereum mainnet gas fees exceeded $200 per transaction. The same transaction on Arbitrum costs under $0.10.
⚠ Controversies & Red Flags
L2 fragmentation has been criticised — liquidity and users are split across dozens of chains, creating a poor user experience and bridging risks.