What is a Layer 2?
A Layer 2 (L2) is a secondary protocol or network built on top of a base blockchain (Layer 1, L1) to increase throughput, reduce fees, or add features while inheriting L1’s security model. L2s solve the blockchain scalability trilemma (security, decentralisation, scalability) by offloading computation off-chain while anchoring final state and disputes back to L1. Ethereum’s L2 ecosystem is the most mature (Arbitrum, Optimism, Base, zkSync, Starknet, Polygon zkEVM).
L2 categories
- Optimistic rollups (Arbitrum, Optimism, Base): assume validity, allow fraud-proof challenge ~7 days; mature EVM compatibility.
- ZK rollups (zkSync, Starknet, Polygon zkEVM, Linea, Scroll): validity proofs guarantee correctness; faster finality.
- State channels (Lightning Network on Bitcoin): off-chain payment channels with on-chain settlement; ideal for high-frequency micropayments.
- Sidechains (Polygon PoS, Gnosis Chain): independent consensus, periodic L1 checkpoints; not strictly L2 by latest definitions but historically grouped.
- Validiums and Volitions: hybrid data availability — off-chain DA with L1 proof.
L2 fragmentation and interoperability
The proliferation of L2s creates liquidity fragmentation and UX friction. Solutions include canonical bridges (slow, trustless), third-party bridges (faster, trust assumptions), aggregator routers (Across, Hop, LayerZero), and emerging cross-rollup settlement layers (Polygon AggLayer, Optimism Superchain, Arbitrum Orbit). EIP-4844 (March 2024) reduced L2 costs by ~90% via dedicated blob data availability.
Türk geliştirici ve yatırımcı bağlamı
Türk DeFi katılımcıları için L2’lere (Arbitrum, Base, Optimism) geçiş gas tasarrufu açısından çekicidir. Yerel CASP’ler (Btcturk, Binance TR, Paribu) çoğu büyük L2’yi yatırma/çekme ağı olarak destekler. 7518 sayılı Kanun (2024) CASP düzenlemesi L1/L2 ayrımı yapmaz; aynı KYC/AML yükümlülükleri uygulanır. Türk projeleri için L2 (Polygon, Base) deployment cazip; L1 (Ethereum mainnet) gas maliyeti küçük protokoller için yasaklayıcı olabilir.
Do: compare L2 security models (canonical bridge withdrawal time, sequencer decentralisation, fraud-proof status); prefer L2s with mature ecosystem and high TVL.
Don’t: assume all L2s share L1 security equally — sidechains and “L2” marketing terms often hide different trust models; verify in L2Beat risk dashboards.