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ETH bridging

Ether (ETH) is the native currency of Ethereum and all Arbitrum chains. It is used to pay the necessary fees to execute a transaction in those chains. Bridging ETH from Ethereum (parent chain) to an Arbitrum chain (child chain) follows, thus, a different process than the one followed when bridging other types of asset.

Depositing ether​

To move ETH from the parent chain to the child chain, you execute a deposit transaction via Inbox.depositEth. This transfers funds to the Bridge contract on the parent chain and credits the same funds to you inside the Arbitrum chain at the specified address.

function depositEth(address destAddr) external payable override returns (uint256)
warning

If the transaction is sent by a 7702-enabled account, the destination address on L2 is subject to address aliasing. The ETH will be credited to the aliased address of the sender, not the raw msg.sender. See address aliasing for details.

The following diagram depicts the process that funds follow during a deposit operation.

Depositing Ether

As far as the parent chain is concerned, all deposited funds are held by the Arbitrum Bridge contract. Once finalized, the ETH becomes available on the L2 at the aliased or specified address, depending on the sender type.

Withdrawing ether​

Withdrawing ether can be done using the ArbSys precompile's withdrawEth method:

ArbSys(100).withdrawEth{ value: 2300000 }(destAddress)

Upon withdrawing, the Ether balance is burnt on the Arbitrum side, and will later be made available on the Ethereum side.

ArbSys.withdrawEth is a convenience function equivalent to calling ArbSys.sendTxToL1 with empty calldataForL1. Like any other sendTxToL1 call, it will require an additional call to Outbox.executeTransaction on the parent chain after the dispute period elapses for the user to finalize claiming their funds on the parent chain (see Child to parent chain messaging). Once the withdrawal is executed from the Outbox, the user's ETH balance will be credited on the parent chain.

The following diagram depicts the process that funds follow during a withdraw operation.

Withdrawing Ether