Crypto Gloss

Based Rollup

A based rollup is a Layer 2 rollup in which transaction ordering is handled not by a dedicated sequencer (the standard model used by Optimism, Arbitrum, and most current rollups) but by Ethereum L1 validators (block proposers) directly. In a based rollup, L2 transactions are included in the L1 block construction process itself — Ethereum validators sequence the L2 along with L1 transactions, with no separate centralized ordering party. The term was popularized by Justin Drake in a 2023 Ethereum Research post, and the concept is positioned as the most decentralization-pure rollup design: if you trust Ethereum L1’s liveness and censorship resistance, a based rollup inherits those properties without requiring additional trust in a separate sequencer. The primary tradeoff is that L1 validators don’t have the specialized context to optimize L2 throughput or MEV as aggressively as a dedicated sequencer — so based rollups may have lower peak throughput and less predictable block timing than sequencer-based rollups.

How It Works

The following sections cover this in detail.

Standard Rollup (Sequencer-Based)

In most current rollups:

  1. Users submit transactions to a sequencer — a dedicated server operated by the rollup team (Optimism, Arbitrum, etc.)
  2. The sequencer orders transactions and publishes ordered batches to Ethereum
  3. The rollup settles on L1 via these batches

Risk: The sequencer can censor users, go offline (causing liveness failure), or charge high MEV. Users must trust the sequencer or wait for fraud proof challenges.

Based Rollup

In a based rollup:

  1. Users submit transactions to L1 Ethereum (or a permissionless L1-included preconfirmation system)
  2. L1 block proposers (Ethereum validators) include L2 transactions in L1 blocks as part of their normal block-building process — often via PBS builders who also handle L2 sequencing
  3. The L2 derives its canonical transaction order from the L1 block order
  4. No separate sequencer exists — the rollup simply reads L1 blocks to determine transaction ordering

Key property: If Ethereum L1 is live and non-censoring, the based rollup is live and non-censoring — no additional party can break these guarantees.

Based Rollup vs. Standard Rollup

Property Standard Rollup Based Rollup
Sequencer Dedicated (centralized) L1 validators (Ethereum itself)
Liveness dependency Rollup team + L1 L1 only
Censorship resistance Sequencer trust required Inherits L1 guarantee
Throughput optimization High (specialized sequencer) Lower (L1 validators not L2 experts)
MEV capture Sequencer captures L2 MEV L1 builders capture; can flow to L1
Preconfirmations Sequencer can give fast confirmations Requires preconf. protocol add-on
Decentralization Lower Higher

Based Preconfirmations

A practical concern with based rollups: Ethereum blocks finalize in ~12 seconds. If a user submits an L2 transaction, they may wait a full 12 seconds to know if it’s included. This is worse UX than a centralized sequencer giving instant soft confirmations.

Based preconfirmations address this: L1 validators can optionally sign “preconfirmation” messages assuring users their transaction will be included in their upcoming block proposal — essentially a validator’s commitment. Protocols like EigenLayer (via restaking) or dedicated preconfirmation modules can provide slashable guarantees for these preconfirmations.

This is an active research area — based rollups with preconfirmations aim to match sequencer-based UX while maintaining L1-level liveness guarantees.

Based Rollups and MEV

In sequencer-based rollups, the sequencer captures L2 MEV — transaction ordering within the rollup is controlled by the sequencer, which can run sandwiches, arbitrage, or auction order flow. This MEV flows to the rollup operator.

In a based rollup, L2 MEV is captured by L1 PBS builders who include L2 transactions in their L1 block construction. This MEV flows back into the L1 PBS ecosystem — potentially returned to L1 validators as bid revenue. This “MEV revenue recycling” to L1 is sometimes cited as a mechanism to strengthen Ethereum L1’s economic security.

Notable Based Rollup Projects

  • Taiko — The most prominent based rollup; uses Ethereum L1 proposers for transaction ordering with its own proving system. Mainnet launched 2024.
  • Based OP Stack — Research proposals for making Optimism-stack rollups based; not yet mainnet deployed.
  • Espresso (shared sequencer) — A related but distinct approach: shared sequencers provide ordering for multiple rollups without being L1-native, contrasting with pure based rollup design.

History

  • 2023, March — Justin Drake coins “based rollup” in an Ethereum Research post, defining the concept and its L1 liveness inheritance property.
  • 2023 — Intense research discussion on based vs. sequencer vs. decentralized sequencer (shared sequencer) rollup designs — framed as the “rollup sequencer wars.”
  • 2023–2024 — Taiko launches its based rollup mainnet — the first production based rollup on Ethereum.
  • 2024 — Based preconfirmation research intensifies following Pectra and restaking ecosystem growth; multiple preconf. protocol proposals published.
  • 2025 — Based rollup design gains traction as an alternative to centralized sequencers amid ongoing regulatory and censorship concerns.

Common Misconceptions

“Based rollups are slower than standard rollups.”

Based rollups have the same ~12-second block time as Ethereum L1, without sequencer soft confirmations. But with based preconfirmations, effective user-experienced latency can approach sequencer-based speeds. The “slow” concern is about UX without preconfirmations, not throughput capacity.

“Based rollups have no sequencer at all.”

L1 proposers (Ethereum validators) are the sequencers in a based rollup — they just happen to also be L1 validators. The “no separate sequencer” framing means no dedicated third party, not that ordering happens magically.

“All future rollups will be based rollups.”

Based rollups have real tradeoffs — complex preconfirmation infrastructure, less throughput optimization, L2 MEV captured by L1 builders rather than the rollup. Many rollup teams believe specialized sequencers (even decentralized ones) offer better overall properties. Based rollups are one design point in a broader spectrum.

Criticisms

  1. Preconfirmation complexity — Guaranteeing fast transaction confirmation without a centralized sequencer requires sophisticated preconfirmation protocols with slashing conditions — adding significant system complexity.
  2. Lower throughput ceiling — L1 validators optimize for L1 revenue, not L2 throughput. A specialized L2 sequencer can apply knowledge of the rollup’s state to pack blocks more efficiently.
  3. MEV extraction by L1 builders — Routing L2 MEV to L1 PBS builders benefits L1 but doesn’t necessarily protect L2 users from MEV any better than a sequencer would.
  4. Limited production track record — As of 2025, based rollups have limited mainnet history compared to years of production data from Optimism, Arbitrum, and other sequencer-based rollups.

Social Media Sentiment

Based rollups generated significant Ethereum researcher Twitter/X discussion in 2023–2024 — Justin Drake’s evangelism and Taiko’s launch kept the topic prominent. Rollup teams at Optimism and Arbitrum were cautiously skeptical, pointing to preconfirmation complexity and throughput concerns. Ethereum decentralization advocates generally support the concept. The debate between “based” vs. “shared sequencer” vs. “decentralized sequencer” is a technical staple of rollup-focused discussions. r/ethereum treats based rollups as intellectually interesting infrastructure research; mainstream crypto audiences rarely discuss the topic.

Related Terms

Sources