Layer 3 (L3)

A layer 3 stacks one more level on top of the rollup model. Its sequencer posts batches and proofs to a layer 2, which in turn settles on Ethereum. Frameworks like Arbitrum Orbit, the OP Stack and ZK chain stacks make it straightforward to deploy one, often through a rollup-as-a-service provider, and many L3s post their data to cheaper external data availability layers.

Projects choose an L3 to get very low fees, their own gas token, custom rules or privacy settings, and dedicated throughput that is not shared with other apps. Gaming chains and social or community chains have been the most visible examples, and some L2s actively court L3s because they bring transactions and fees to the parent chain.

Critics argue that L3s add little that a well-designed L2 cannot offer, while stacking extra trust assumptions: users depend on the L3 operator, the L2 bridge and Ethereum, and exiting can mean two withdrawal delays. Liquidity also fragments further, and several L3s have seen activity fade after launch incentives ended.