A Based Rollup is a type of Ethereum Layer 2 rollup that relies on Ethereum’s own block proposers to sequence Layer 2 transactions instead of using a separate sequencer controlled by the rollup. The model is also known as L1-sequenced or L1-based sequencing because transaction ordering and rollup block production are closely integrated with Ethereum’s Layer 1 infrastructure.
Rollups are designed to increase blockchain capacity by executing transactions outside Ethereum’s main execution layer and publishing enough information to Ethereum for settlement and verification. Most rollups use dedicated sequencing infrastructure to decide which transactions are included and in what order. This can provide fast confirmations and considerable control over the user experience, but it introduces another component that users must depend on.
Based Rollups take a different approach. Rather than creating an independent sequencing mechanism, they allow Ethereum block proposers and related block-building infrastructure to determine the ordering of rollup transactions. Ethereum therefore performs part of the job that a dedicated Layer 2 sequencer would normally perform.
The term “based rollup” was introduced by Ethereum researcher Justin Drake in 2023. The idea attracted attention because it offers a way to inherit more of Ethereum’s liveness and decentralisation properties while simplifying the sequencing architecture of a rollup.
How Based Rollups Use Ethereum for Sequencing
To understand a Based Rollup, it helps to separate sequencing from execution. A rollup still performs Layer 2 execution and maintains its own state. What changes is the mechanism responsible for determining the order in which transactions become part of the rollup.
Many conventional rollups operate a sequencer. Users send Layer 2 transactions to this sequencer, which orders them, produces Layer 2 blocks and eventually submits relevant information to Ethereum. In early rollup deployments, the sequencer is often operated by the development team or another designated entity.
A Based Rollup removes the need for this privileged Layer 2 sequencing role. Transaction sequencing is instead connected to Ethereum’s block production process. Ethereum proposers can include rollup-related transactions as part of the blocks they propose, allowing Layer 1 to determine the canonical ordering.
A simplified process can be described as follows:
- Users create transactions intended for the Based Rollup.
- These transactions or bundles are made available to Ethereum’s block-building infrastructure.
- An Ethereum block proposer selects a Layer 1 block containing the relevant rollup data.
- The ordering established through the Ethereum block becomes authoritative for the rollup.
- The rollup executes the ordered transactions and updates its Layer 2 state according to its own rules.
- Ethereum continues to provide the underlying data availability and settlement guarantees required by the rollup architecture.
This does not mean that all Layer 2 computation suddenly moves back to Ethereum. Doing so would defeat the scalability benefits of rollups. Execution remains associated with the Layer 2 system, while Ethereum assumes the sequencing role that would otherwise require dedicated rollup infrastructure.
The distinction is important. A Based Rollup is still a rollup and still scales Ethereum by processing activity outside the main chain’s normal execution environment. It is “based” because its sequencing mechanism is based directly on Ethereum.
Based Rollups vs Rollups with Centralised Sequencers
The sequencing model has consequences for decentralisation, liveness, economics and user experience. A dedicated sequencer can be highly optimised for one rollup, but it also creates infrastructure that must remain available and behave correctly.
A comparison shows where the architectures differ.
| Characteristic | Based Rollup | Rollup with Centralised Sequencer |
| Primary sequencing | Ethereum L1 infrastructure | Dedicated L2 sequencer |
| Privileged sequencer | Not required | Usually present |
| Liveness dependency | Primarily Ethereum | L2 sequencer plus fallback mechanisms |
| Transaction ordering | Connected to L1 block production | Determined by the L2 sequencer |
| Sequencer failure risk | Reduced as a separate L2 risk | Sequencer outage can interrupt normal operation |
| Sequencing decentralisation | Inherits Ethereum’s proposer set | Depends on the rollup’s sequencer architecture |
| Sequencing revenue | Can flow into Ethereum’s block-building economy | Can be captured by the rollup sequencer |
| Confirmation experience | Depends on implementation and preconfirmation mechanisms | Can provide very fast sequencer confirmations |
The strongest argument for Based Rollups is credible neutrality in sequencing. A rollup does not need to build a new decentralised sequencer network or depend indefinitely on a single operator. Ethereum already has a distributed validator set and a functioning block production system.
Liveness is another advantage. If Ethereum continues producing blocks, the basic sequencing mechanism for a Based Rollup can continue functioning. A conventional rollup may implement forced transaction inclusion or an L1 escape mechanism for sequencer failures, but normal operation can still be affected when its sequencer goes offline.
The model can also strengthen the economic relationship between Ethereum and its Layer 2 ecosystem. Sequencing has economic value because control over transaction ordering can generate fees and MEV, or maximal extractable value. With based sequencing, more of that activity can remain connected to Ethereum’s existing proposer and block-building economy instead of being captured entirely by a separate Layer 2 sequencer.
Why Based Rollups Are Attractive for Ethereum
Ethereum’s rollup-centric scaling strategy has produced a large Layer 2 ecosystem, but it has also created new infrastructure layers. Individual rollups can have their own sequencers, bridges, proving systems, governance structures and transaction pipelines. As a result, scaling Ethereum does not automatically mean inheriting every decentralisation property of Ethereum itself.
Based sequencing attempts to minimise one of these differences.
Its main potential advantages include:
- Ethereum-level sequencing liveness without requiring a separate decentralised sequencer network;
- reduced dependence on a privileged Layer 2 operator for transaction ordering;
- closer alignment between Layer 2 activity and Ethereum’s validator economy;
- simpler rollup architecture because a separate consensus mechanism for sequencing is unnecessary;
- access to Ethereum’s existing proposer and block-building infrastructure;
- stronger credible neutrality because transaction ordering is not controlled exclusively by the rollup operator.
This approach can be particularly attractive for projects that prioritise Ethereum alignment and minimisation of additional trust assumptions. Instead of recreating decentralised sequencing at Layer 2, the rollup can reuse infrastructure that Ethereum already maintains.
There are also composability implications. If several Based Rollups rely on the same Layer 1 sequencing infrastructure, Ethereum blocks can potentially provide a common coordination point for activity across those rollups. This has encouraged research into synchronous composability and atomic interactions between Layer 2 systems.
Such capabilities are not automatic simply because two networks are Based Rollups. Cross-rollup execution still requires compatible designs and supporting infrastructure. Nevertheless, shared sequencing through Ethereum provides a common foundation that independently sequenced rollups do not naturally possess.
Limitations and the Role of Preconfirmations
Based sequencing involves trade-offs. One of the most important concerns is confirmation speed.
A centralised Layer 2 sequencer can provide users with a preliminary confirmation almost immediately after receiving a transaction, even before the transaction is ultimately settled through Ethereum. A basic Based Rollup that waits for Ethereum block production cannot necessarily provide the same experience. Ethereum’s slot time is approximately 12 seconds, which can feel slow for applications such as trading, gaming or payments that benefit from near-instant feedback.
Preconfirmations, often shortened to preconfs, are being developed as one way to address this issue. A preconfirmation provides a commitment that a transaction will be included or executed under specified conditions before the relevant Ethereum block receives full confirmation.
The broader challenges for Based Rollups include:
- delivering low-latency confirmations without reintroducing a highly trusted intermediary;
- designing efficient preconfirmation markets and enforcement mechanisms;
- managing MEV created through Layer 1 sequencing;
- integrating rollup transactions efficiently with Ethereum block builders and proposers;
- achieving cross-rollup composability without creating additional coordination risks;
- competing on user experience with rollups that operate highly optimised dedicated sequencers.
Based Rollups therefore do not make sequencing complexity disappear. They move sequencing closer to Ethereum and change where that complexity is handled.
The model also does not determine whether a rollup uses optimistic or zero-knowledge proofs. “Based” describes the sequencing architecture, not the mechanism used to prove or verify the correctness of Layer 2 state transitions. In principle, based sequencing can be combined with different rollup proof systems.
The Role of Based Rollups in Ethereum Scaling
Based Rollups represent an attempt to scale Ethereum while retaining more direct dependence on Ethereum itself. This distinguishes them from approaches that increase throughput by creating increasingly independent Layer 2 infrastructure.
The idea is significant because decentralising a rollup sequencer is technically difficult. Building another validator or sequencer network can introduce new tokens, incentives, consensus rules and security assumptions. Based sequencing offers an alternative: use Ethereum’s existing decentralised block production instead of constructing another sequencing consensus system.
Projects exploring the model include Taiko, which has made based sequencing a central part of its Layer 2 architecture. Research around Based Rollups has also expanded into preconfirmations, shared sequencing and mechanisms for improving interoperability between Ethereum rollups.
Whether Based Rollups become a dominant Layer 2 architecture will depend partly on their ability to match the speed and convenience offered by dedicated sequencers. The decentralisation benefits are meaningful, but users also expect inexpensive transactions and fast confirmations.
For Ethereum, the larger idea is straightforward. A rollup does not necessarily need to create its own authority for deciding transaction order. By allowing Ethereum to perform that function, a Based Rollup can inherit more of the base layer’s liveness, neutrality and economic security while still moving execution away from Layer 1.