Pre-confirmations (pre-confs) are commitments — made by a sequencer, validator, or block proposer — guaranteeing that a transaction will be included in a future block and executed as specified. They give users near-instant feedback without waiting for full on-chain finality.
They don’t replace finality; they provide credible, fast soft-finality ahead of it.
The Finality Problem
Ethereum L1 finality takes ~13 minutes (two epochs). L2 rollups typically achieve sequencer confirmation in seconds but full L1 settlement in minutes to days.
For many applications, waiting even a few seconds for a sequencer confirmation feels slow compared to Web2:
- Visa card transactions: <1 second perceived
- CEX order fills: <100ms
- Ethereum sequencer confirmation: 1–3 seconds
- L1 finality: ~13 minutes
Pre-confs push the user experience closer to CEX speed while retaining decentralized infrastructure.
How Pre-Confirmations Work
- User submits transaction
- Sequencer or validator evaluates it — checks fee, validity, conflicting transactions
- Sequencer issues a signed commitment — “I will include this tx in block N at position X”
- User receives the commitment — near-instant response
- Block is built — the sequencer follows through; if not, they can be slashed
The commitment is only as trustworthy as the slashing condition backing it. That’s what separates pre-confs from raw sequencer promises.
Slashing and Credibility
For pre-confs to be credible, sequencers must have skin in the game:
- Optimistic pre-confs: Trust the sequencer; disputes resolved after the fact
- Preconf with restaking: Sequencers restake ETH via EigenLayer; breaking a pre-conf commitment → slashing
- EspressoSystems, Bolt: Building restaking-backed pre-conf infrastructure
Without slashing, a pre-conf is just a “best effort” signal — useful but not credible.
Based Pre-confirmations
A specific design where L1 validators (not just L2 sequencers) issue pre-confs. This is part of the based rollup architecture where Ethereum validators sequence L2 transactions:
- The L1 block proposer who will propose the next block issues pre-confs for transactions they intend to include
- Users get guaranteed L1 inclusion at near-L1 speed
- Eliminates centralized sequencer reliance
This is being actively researched as part of Ethereum’s roadmap.
Use Cases
| Use Case | Why Pre-Confs Help |
|---|---|
| Trading / DEX | Near-instant fill confirmation |
| Payments | Real-time confirmation for merchants |
| Gaming | Actions confirmed without lag |
| Intent settlement | Solvers need fast confirmation their fill is accepted |
Key Projects
- Espresso Systems — Shared sequencing + pre-confirmation network
- Bolt (Chainbound) — Pre-confirmation for Ethereum validators
- Primev — MEV-aware block building with pre-conf infrastructure
Sources
- Ethereum Research: “Based preconfirmations” by Justin Drake
- EspressoSystems documentation
- Bolt by Chainbound: preconf protocol specification