Based Rollup

A based rollup is a type of layer 2 blockchain in which the ordering of transactions, known as sequencing, is handled by the validators of the underlying layer 1 chain rather than by a separate operator. On Ethereum, this means that the same block proposers who build ordinary Ethereum blocks also decide which rollup transactions are included and in what order. The term "based" was popularised by Ethereum researcher Justin Drake in 2023, and such designs are also called layer 1 sequenced rollups.

Most rollups today use a centralized sequencer run by the team behind the network. A based rollup removes that role, inheriting the layer 1's decentralization and liveness at the cost of slower confirmations and less control over fees. It can be built as an optimistic rollup or as one of the zero-knowledge rollups; "based" describes who orders transactions, not how they are proved.

Think of a busy city with one main post office and several smaller courier services. Most couriers have their own sorting room where a manager decides which parcels go first, then hand the sorted bags to the main post office for delivery. If the manager is ill, or decides to favour certain customers, the courier's customers suffer.

A based rollup is a courier that has no sorting room of its own. It lets the main post office's staff sort its parcels along with everything else. Customers get the same fairness and reliability as the main post office, with no single manager in charge. The price is that the courier can no longer promise its own instant receipts, because it depends on the main office's timetable.

In a standard rollup, users send transactions to a sequencer, which orders them, gives users a quick confirmation, and later posts batches of data to the layer 1. In a based rollup the flow changes:

1. Submission. Users or searchers submit rollup transactions to the layer 1's public pool or to block builders.
2. Ordering on layer 1. When a layer 1 proposer builds its next block, it includes rollup batches, which fixes their order at the same moment the layer 1 block is produced.
3. Execution. Rollup nodes read the batches from layer 1 and compute the new rollup state.
4. Proving. Depending on the design, validity proofs or a fraud-proof window confirm that the new state is correct.

Because sequencing is merged into layer 1 block building, the value that can be extracted by ordering transactions flows mainly to layer 1 proposers and builders, rather than to a rollup operator.

Supporters point to several advantages:

• Inherited liveness. The rollup keeps working as long as the layer 1 does, with no single sequencer that can go offline or censor users.
• Simplicity. There is no separate sequencer network, consensus process or token needed to decentralize ordering.
• Composability. Because several based rollups share the same sequencer set, it becomes possible in principle to combine actions across them, and with layer 1, in a single block, improving composability.
• Alignment. Fees and ordering value support the layer 1's validators, which some see as good for the Ethereum blockchain as a whole.

The main drawback is speed. Ethereum produces a block every 12 seconds, so a based rollup's transactions are only confirmed at that rhythm, compared with sub-second confirmations from centralized sequencers. Researchers have proposed preconfirmations, in which layer 1 proposers make signed, collateral-backed promises to include a transaction, to close this gap. Based rollups also give up revenue the operator could earn from sequencing, which matters for projects that rely on such income, and they are exposed to the front-running and transaction ordering practices of layer 1 block builders. Finally, the design is still young, and tools for cross-rollup composability are largely experimental. The wider debate about scaling solutions includes these issues alongside the blockchain trilemma.

Taiko, an Ethereum-compatible zero-knowledge rollup whose main network launched in 2024, is the best-known based rollup, using Ethereum proposers for sequencing while experimenting with multiple types of proof. Other teams have announced based designs or are researching shared sequencing that sits between the two models. Development work on Ethereum itself, including changes to how proposers and builders interact, affects how practical preconfirmations become. As of November 2026, based rollups remain a small part of total rollup activity, while larger networks such as those in the Optimism Superchain and Arbitrum ecosystems still rely on operator-run sequencers with plans to decentralize them over time. The concept has nonetheless shaped debate about how layer 2 networks should relate to Ethereum and to the Ethereum Virtual Machine ecosystem.

• Ethereum Research forum
• Taiko