Move ETH From Base to Ethereum: 7-Day Bridge or Minutes

ETH on Base can reach Ethereum mainnet through the official bridge in about a week, or through a cross-network swap in minutes. The official route is part of the OP Stack that Base is built on: you start a withdrawal on Base, prove it on Ethereum, wait out a seven-day challenge period and finalise it with a third transaction. A swap needs one transfer: send ETH on Base to the order's deposit, receive ETH on mainnet. On KOT.CASH the swap minimum is about 0.0123 ETH, the provider waits for 30 Base blocks — one minute — and pays out minus about 0.0003 ETH.

The official withdrawal, on a timeline

• Day 0, minute 0 — you initiate the withdrawal on Base (Base gas, a few cents).
• About one hour later — the withdrawal can be proven on Ethereum once the Base output containing it has been posted. You submit the prove transaction (Ethereum gas).
• Day 7 — the challenge period for the proven withdrawal ends. With fault proofs live on Base since 2024, anyone could have disputed an invalid state during that window.
• Day 7, any time after — you submit the finalise transaction on Ethereum (Ethereum gas again) and the ETH appears in your mainnet wallet.

The bridge UI on Base's site and wallets such as Coinbase Wallet walk you through these steps, but you have to come back twice. Two of the three transactions are on Ethereum, so on a busy day the bridge is not free: prove and finalise together often use 300,000–500,000 gas.

The swap, on the same timeline

1. Minute 0 — choose ETH on the Base network to send and ETH on Ethereum to receive, enter at least about 0.0123 ETH, paste your mainnet address (the same 0x address is fine) and create the order.
2. Minute 1 — send ETH on Base to the deposit address. Base produces a block every two seconds, so 30 confirmations take about a minute.
3. Minutes 2–6 — the provider processes the order (estimated 2–4 minutes) and sends ETH on mainnet.
4. Minute 6–7 — the payout is in an Ethereum block. It is final after two epochs, about 13 minutes; most wallets show it as confirmed right away.

Cost comparison for 0.1 and 1 ETH

The bridge's cost does not depend on the amount; the swap's does. At low gas the bridge is cheaper for any amount if you can wait a week. At high gas, small and medium transfers are cheaper as a swap. The gas fee calculator prices the two L1 bridge transactions at today's gwei.

Base specifics worth knowing

• Base has no token of its own. Gas is paid in ETH, and Base ETH is the same asset economically but sits on a different network.
• Base uses chain ID 8453. Wallets add it automatically from apps; check the network label before sending.
• Exchanges increasingly allow ETH withdrawals directly on Base. If your destination is an exchange that accepts Base deposits, you may not need mainnet at all.
• Superchain networks (Optimism, Base, and other OP Stack chains) share the same seven-day withdrawal model, but their ETH does not move between each other automatically.

Why Base needs only 30 confirmations

A Base block is produced by the sequencer every two seconds and is posted to Ethereum in batches shortly after. Reorganisations of Base blocks that have already been shared by the sequencer are rare, so the provider waits for 30 blocks — a minute — rather than for the batch to be final on Ethereum, which would take around 15–20 minutes. That is a business judgement about risk, the same one exchanges make when they credit Base deposits quickly. The seven-day window, by contrast, only matters for moving value out of Base through the bridge.

When the order page looks stuck

If 30 confirmations do not appear within a few minutes, look up your hash on Basescan. Status Success with the deposit address as recipient means the funds are there and processing is under way. If the transaction does not exist on Basescan, it was sent on another network — usually mainnet or Optimism, because the address format is the same. Do not send again; contact support with the hash. More on reading L2 explorers in Arbiscan and Basescan explained.