Based Rollup

Overview

A based rollup is a rollup that delegates sequencing to Ethereum’s Layer 1 block-production process. In the original definition, a rollup is “based” or “L1-sequenced” when the next Ethereum proposer can permissionlessly include the next rollup block as part of the next L1 block, potentially in collaboration with searchers and builders. The rollup does not depend exclusively on a privileged sequencer to determine transaction order.

Based sequencing can inherit liveness and censorship-resistance properties from Layer 1. If Ethereum continues producing blocks, eligible L1 participants can continue sequencing the rollup according to its rules. It may also simplify credible neutrality and enable tighter forms of interoperability between rollups that share the same L1 ordering environment. These properties do not automatically eliminate all centralization, because transaction submission, proving, bridging, preconfirmation, and governance can still involve separate actors.

The word “based” describes sequencing, not the rollup’s proof system or execution model. A based rollup can use optimistic or validity proofs. It is also different from a native rollup, which concerns whether the L1 directly verifies or executes the rollup’s state transition function. Based sequencing can therefore be combined with several security and execution architectures.

The trade-offs include exposure to Ethereum block timing, L1 congestion, proposer-builder economics, and the challenge of providing fast user confirmations before L1 inclusion. Some designs add preconfirmations or specialized transaction-submission paths to improve latency. Payment applications should distinguish a sequencer acknowledgement from L1 inclusion and final settlement. They should monitor the rollup state commitment, Ethereum transaction, and relevant finality milestone before treating funds as irreversible.