There are two ways to move ETH from Arbitrum One back to Ethereum mainnet. The native Arbitrum bridge is trustless but slow: a withdrawal waits about seven days for the challenge period and then needs a second transaction on Ethereum to claim it. A cross-network swap โ send ETH on Arbitrum, receive ETH on mainnet โ takes minutes and costs a service fee. On KOT.CASH that swap starts at about 0.011 ETH, the provider waits for 120 Arbitrum blocks (around half a minute) and pays out on mainnet minus about 0.0003 ETH of network fee.
Why the official bridge takes a week
Arbitrum is an optimistic rollup. It posts transaction data to Ethereum and assumes the resulting state is correct unless someone proves otherwise during a challenge window. Deposits from Ethereum to Arbitrum arrive in about ten minutes, but withdrawals in the other direction can only be finalised on Ethereum after the window closes โ currently about 6.4 days (45,818 Ethereum blocks), usually described as 'about a week'. Then you return to the bridge and execute the withdrawal on mainnet, paying Ethereum gas for that claim.
Nothing is lost by waiting; it is simply the price of not trusting a third party. For large amounts and no time pressure, the native bridge is the reference option.
The two routes side by side
| Native Arbitrum bridge | Cross-network swap | |
|---|---|---|
| Time | โ 7 days + claim | โ 5โ10 minutes |
| Transactions you sign | 2 (L2 start, L1 claim) | 1 (send on Arbitrum) |
| Fees | Arbitrum gas + Ethereum gas for the claim | 1% / 1.5% service fee + โ 0.0003 ETH payout |
| Minimum | none | โ 0.011 ETH |
| Trust | Ethereum and Arbitrum contracts only | The swap service and its provider |
Third-party bridges sit in between: they front you ETH on mainnet in minutes and are repaid when the slow withdrawal clears, charging a spread for that. Their fees and risks vary, so judge each one separately.
Doing it as a swap
- In the widget, choose ETH on the Arbitrum network as the coin you send and ETH on Ethereum as the coin you receive. The pair is listed like any other.
- Enter the amount (at least about 0.011 ETH) and paste your mainnet address. It can be the same 0x address you use on Arbitrum.
- Choose floating (1%) or fixed (1.5%).
- Send ETH on Arbitrum One to the deposit address. In MetaMask, check the network selector shows Arbitrum One before sending.
- The provider waits for 120 Arbitrum blocks โ Arbitrum produces a block roughly every 0.25 seconds, so that is about 30 seconds โ and processes the order in an estimated 2โ4 minutes.
- ETH arrives on mainnet as a normal transfer. No claim step.
Which is cheaper for your amount
Say you move 0.5 ETH (โ $1,222). The swap costs 1% (0.005 ETH) plus about 0.0003 ETH payout fee โ about $13. The native bridge costs Arbitrum gas (cents) plus the mainnet claim, a contract call that typically uses 100,000โ150,000 gas: at 2 gwei that is 0.0002โ0.0003 ETH, under a dollar; at 20 gwei, $5โ7. For 0.5 ETH and no hurry, the bridge wins by about $10. For 0.05 ETH, the difference is around a dollar, and the week of waiting is usually the bigger cost. The gas fee calculator helps price the claim at today's gwei.
Withdrawing from an exchange instead
If your ETH on Arbitrum came from an exchange and is going back to an exchange, the cheapest route may skip mainnet entirely. Most large exchanges accept ETH deposits on Arbitrum One directly and credit them like mainnet ETH. Check the deposit page for an 'Arbitrum One' network option. Moving to mainnet only makes sense when the destination is a mainnet-only service, a hardware wallet setup you keep on Ethereum, or DeFi that does not exist on Arbitrum.
Arbitrum One vs Arbitrum Nova
Arbitrum has two public chains. Arbitrum One is the rollup where most DeFi and exchange withdrawals land. Arbitrum Nova is an AnyTrust chain built for gaming and social apps, with a data availability committee instead of posting all data to Ethereum. The provider's ARBITRUM network is Arbitrum One. ETH on Nova needs its own route.
Things that go wrong
- Sending from mainnet instead of Arbitrum. The deposit address is watched on Arbitrum; a mainnet transfer to it never reaches the order. Contact support with the hash if it happens.
- Leaving no ETH on Arbitrum for gas. Arbitrum gas is cheap but not zero. Keep 0.0005 ETH if you plan more transactions there.
- Expecting a bridge claim. With a swap there is nothing to claim. If a site asks you to 'claim' or sign a message for your swap payout, it is not ours.
FAQ
How long does an Arbitrum withdrawal to Ethereum take?
Through the native bridge, about seven days (the challenge period) plus a claim transaction on Ethereum. A swap takes minutes.
What is the minimum for an Arbitrum ETH to mainnet ETH swap?
About 0.011 ETH at the time of writing.
Can I use the same address on Arbitrum and Ethereum?
Yes, an EVM wallet uses the same 0x address on both networks.
Is a swap safe compared with the official bridge?
The native bridge relies only on Arbitrum's and Ethereum's contracts. A swap relies on the service and its liquidity provider; it trades that trust for speed.
Does this work for Arbitrum Nova?
No. The ARBITRUM network in the swap is Arbitrum One.