Ethereum client teams are testing an opt-in fast confirmation mechanism that could cut the time some layer-2 networks and exchanges wait to recognize mainnet deposits to about 13 seconds.
The proposed Fast Confirmation Rule (FCR) would reduce “deposit time from Ethereum L1 to L2s or exchanges to about 13 seconds, an 80-98% reduction for most L2s and exchanges,” Ethereum researcher Julian Ma wrote on X.
Most users today rely on canonical bridges, where transfers typically wait for multiple block confirmations or full finality, a process that can take around 13 minutes. However, many exchanges and L2s do not wait for finality, instead relying on “k-deep” confirmation rules, which offer no formal guarantees. In k-deep confirmation, a transaction is considered finalized only after k blocks (with k being a specific number).
Developers say the rule can be adopted without a hard fork, though client and API integration work is still underway. Client teams are already working on implementations, and once deployed, nodes can begin using the rule without network-wide coordination. Exchanges, L2s and infrastructure providers are expected to integrate it with minimal changes.
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How the FCR works
Rather than counting blocks, the FCR evaluates validator attestations to determine whether a block is safe to treat as confirmed, solving the issue of slow bridging.
The FCR makes two assumptions: first, the network is fast enough for validator messages to arrive within seconds, and second, that no single actor controls more than 25% of staked Ether (ETH). These thresholds sit below Ethereum’s stricter finality conditions but are considered sufficient for most real-world use cases.
“When a node detects more security is needed, it waits longer to fast confirm a block. It’s a feature, not a bug,” Ma wrote.
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Ethereum co-founder Vitalik Buterin also voiced support for the mechanism, saying that it can provide a “hard guarantee” that a transaction will not be reverted after a single slot, or about 12 seconds, under certain network conditions.
Concerns remain among community
Not everyone is convinced the FCR will hold up in real-world conditions. X user serx noted that the model leans heavily on trust assumptions, writing that “supermajority honest is carrying a lot of weight there.”
Another user acknowledged the potential upside, noting that near-instant confirmations could significantly improve user experience, but only if those assumptions consistently hold in practice. “Can those assumptions hold under stress?” one user asked.
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