Operation Tutorial: Step by step guide on how to retrieve ETH from Base Chain

Original author: @0x Cygaar

Original translation: Jaleel, cookie, BlockBeats

Editor's note: Over an hour ago, the project behind "$BALD," the "meme dragonhead" on Coinbase's Layer 2 network Base, suddenly withdrew a total of 8,660 ETH and 179 million $BALD liquidity within 7 minutes. The price of $BALD plummeted, with a maximum drop of 80%.

Although the project later added back 400 ETH liquidity within the next half hour, it was not enough to restore shattered confidence. Due to the unavailability of cross-chain deposits and withdrawals on the Base network frontend, panic spread quietly with fears that ETH may not be withdrawn to the mainnet. There were even voices off-market suggesting to purchase ETH on Base network at a discount.

In fact, despite the absence of a frontend deposit and withdrawal page, it is still possible to withdraw ETH cross-chain to the Base network now, so there is no need to panic. However, currently, you need to install git and golang on your PC to run the withdrawal script. Due to the complexity of the process, it is highly recommended to wait for Coinbase to release the official cross-chain bridge frontend. This guide is intended for those who absolutely need to bridge now and do not want to wait for the official bridge UI to be available.

This article was written by @0x Cygaar on July 31st. The following is the original translation by BlockBeats:

Everyone is now claiming that bridging to the Base chain is a one-way process and funds cannot be withdrawn. But is this true?

In fact, we can use the native withdrawal process to retrieve funds back to the mainnet after 7 days. If you need to bridge back to Ethereum, here is an in-depth guide:

The Base chain is essentially a 1-to-1 fork of Optimism, which means we can leverage all the functionalities that OP has. This includes a native withdrawal process that allows you to move ETH from Base back to the mainnet. The downside is that it takes 7 days due to the challenge period.

Why does it take 7 days? Because Optimistic Rollups needs enough time to challenge potential fraudulent claims. Due to this 7 day period, most people will use third-party bridging to bridge back to the mainnet faster. However, the local withdrawal method should always be effective.

Before continuing, please note that the second half of this guide requires you to have git and golang installed on your computer to run a script for withdrawal. If you haven't installed either of them, I suggest waiting for Coinbase to release their official bridging frontend.

First, you need to access the L2 StandardBridge contract at this location: https://basescan.org/address/0x4200000000000000000000000000000000000010.... Go to the contract section and click on "Write as Proxy". Scroll down to "withdraw" or "withdrawTo". The only difference between the two is that the latter allows you to choose the destination address to receive ETH on the mainnet.

Here's how you should fill in the fields:

1) withdraw - This is the amount of ETH you want to bridge back to the mainnet.

2) _l2 Token - Use the value 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000. This is the ETH token address on Base.

3) _amount - This should be the same value used in Part 1, but converted to wei. You can use the following link to convert: https://eth-converter.com

4) _minGasLimit - Enter 0

5) _extraData - Enter 0x

Submit the transaction and save the transaction hash. We will mention it later.

Before I explain the next step, let's briefly talk about how OP handles withdrawals. After the Bedrock upgrade, users need to do two things before withdrawing. First, they need to submit proof to L1 that they made a withdrawal on L2 (in this case, Base).

After this, users must wait 7 days to give any external parties the opportunity to challenge the proof. If no challenges occur, users can complete the withdrawal on L1. There is a nice user interface on the OP mainnet to facilitate this, but for Base, we will use a command-line tool.

Here is the command-line tool for withdrawing created by the Base team: https://github.com/base-org/withdrawer (special thanks to @steveklbnf). Clone the repository locally and run "go install" in the folder. You should be able to execute the withdrawal command.

The README explains what needs to be done, but essentially you will run the withdrawal command with the necessary inputs - the transaction hash mentioned above, an RPC URL (you can use Alchemy/Infura), and the private key of the withdrawal account (never share your private key anywhere). After running this command, you will receive a transaction hash. You can confirm that your proof has been accepted by searching for this transaction hash on Etherscan (for the mainnet).

Then, you will have to wait for 7 days before proceeding. Once this challenge period is over, you can execute the second command in the README to complete the withdrawal. It's very likely that an official user interface will be released before that, which will make this process easier.

The OP tech stack always has a bridging mechanism to return from L2 to L1, and they have specifically created a user interface to simplify this process. This guide is applicable to all OP tech stack chains. For a comprehensive explanation of the withdrawal process, please read more here: https://community.optimism.io/docs/protocol/withdrawal-flow/#

This is the complete information on how to withdraw ETH from the Base chain before the official bridging UI is live. Withdrawing ETH from the Base chain is not particularly difficult, but it does require some technical knowledge at the moment. Again, it's important to note that this guide is intended for those who absolutely need to bridge now and don't want to wait for the official bridging UI.