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What is a based rollup?
A based rollup is a rollup with no sequencer of its own: the main chain's block proposers order its transactions. The next layer 1 proposer can include the next rollup block in its own block without anyone's permission, so the rollup inherits the main chain's ordering and uptime.
What it means for you
On a based rollup, no single operator can stop your transactions or stall the chain unless the main chain itself stalls, which removes a common rollup failure point. The trade-offs are that confirmations follow the main chain's pace unless extra pre-confirmation schemes are added, and ordering value (MEV) goes to main-chain proposers rather than the rollup.
How it works
In Justin Drake's proposal on Ethereum Research, a rollup is based, or L1-sequenced, when its sequencing is driven by the base layer 1: the next L1 proposer, working with L1 searchers and builders, can permissionlessly include the next rollup block. Listed advantages: the rollup inherits L1 liveness and decentralization, needs no escape hatch for sequencer failure, reuses existing builder infrastructure and is simpler than even centralized sequencing. Listed disadvantages: the rollup gives up MEV income to the L1, cannot easily offer fast pre-confirmations, and some ordering services, such as first-come-first-served, become hard to build.
Source: Based rollups: superpowers from L1 sequencing (Justin Drake, Ethereum Research) · checked 4 October 2026
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