TL;DR
A bridge from any supported chain delivers ETH on Base in roughly 2 seconds, fast enough that the funds are usable before you switch tabs.
The speed comes from a relayer fronting your ETH on Base out of its own capital the moment you deposit, not from waiting on any chain to finalize.
The relayer is reimbursed later through background settlement: fills are aggregated into root bundles proposed roughly every 1.5 hours minimum and verified by UMA's Optimistic Oracle. You never wait for this part.
Across is built by Risk Labs, runs on 20+ chains including Base (chain ID 8453), has processed billions in volume since 2021, and has never had a protocol-level exploit.
Intro
The fill lands in about two seconds. You sign a deposit on Arbitrum, Optimism, Ethereum, or any of the other supported chains, and ETH shows up in your wallet on Base before the page finishes confirming. To bridge ETH to Base on Across is to wait about as long as a single block on a fast chain, not the minutes or multi-day windows older bridges trained you to expect.
That number is not a marketing rounding. It falls out of how the protocol is built, and the mechanism is the opposite of what most people assume a bridge does.
A Relayer Fronts Your ETH Before Any Chain Finalizes
A traditional bridge makes you wait for the source chain to finalize, then mints or releases funds on the destination. Across does not work that way. It is an intents protocol: you declare an outcome (ETH on Base, this amount, this address), and a competitive network of relayers races to make that outcome true.
Here is the sequence when you send ETH to Base.
You deposit ETH on the origin chain. The protocol escrows your input in the origin SpokePool and emits an event describing exactly what you want delivered on Base.
Relayers watching that event compete to fill it. The winning relayer calls the fill on Base's SpokePool using its own ETH, not yours, and the ETH arrives at your address in roughly 2 seconds.
Your part is over. The ETH on Base is real, spendable, and yours. You can swap it, supply it, or pay gas with it immediately, because on Base ETH is the native gas token.
The relayer has now spent its own capital to satisfy your intent, and it holds the claim on your escrowed deposit. It gets made whole during settlement. That part happens entirely in the background.
The Dataworker batches every fill across all chains over a window, matches each fill on Base against its original deposit, and proposes the reconciliation as a set of merkle roots (a root bundle) to the HubPool on Ethereum. That proposal posts a bond and enters a challenge period secured by UMA's Optimistic Oracle, the same optimistic verification UMA has run for years. If no one disputes it, the bundle finalizes and relayers are repaid. Bundles are proposed roughly every 1.5 hours at minimum, and the cost of settling one stays flat no matter how many fills it covers.
The point of the design is who waits. The relayer absorbs the finality risk and the settlement delay. You do not. By the time the slow, careful part of the system runs its course, you have already moved on with ETH on Base in hand.
This holds up because Across runs a 1-of-N honest actor model. As long as a single honest participant is watching, a bad bundle proposal gets disputed and thrown out. The protocol has settled billions in volume across 20+ chains since 2021 with no protocol-level exploit.
How to Bridge ETH to Base
Open the Across Base bridge and connect your wallet.
Pick your origin chain and enter the amount of ETH to move. Across supports ETH from chains like Ethereum, Arbitrum, Optimism, and more, all routing to Base (chain ID 8453).
Confirm the quote and sign the deposit. That single signature is the only thing you wait on.
Watch ETH arrive on Base in about 2 seconds. It is immediately usable as gas and as a tradeable balance.
There is no wrapped placeholder token to redeem and no separate claim step. You receive native ETH on Base.
The Official Base Bridge Makes You Wait for the Machinery
Base is an OP Stack rollup that settles to Ethereum, with ETH as its gas token. Its canonical bridge is correct and trustworthy. But it is built around chain mechanics, not around your wait time. A canonical deposit moves at the pace of the underlying messaging, and withdrawals back to Ethereum from an OP Stack rollup sit behind a multi-day fault-proof window before funds release.
For getting ETH onto Base, the difference is who eats the delay. Across puts a relayer's capital in front of chain finality, so the relayer waits and you do not. The trust assumptions are different, which is the whole reason the security model matters. You can read how settlement is verified in the Across intent lifecycle docs.
Two Seconds Means the Bridge Stops Being a Step
At two seconds, bridging is no longer something you plan around. You do not move ETH to Base and then circle back later to do the thing you actually came for. The ETH is on Base, native and spendable, before you have switched tabs to the app you were headed for.