Thread by @0xCygaar

Everyone is claiming that bridging into Base chain is a one way process with no way to withdraw funds.

This is not true.

You can use the native withdrawal process to get your funds back on mainnet (7 days).

If you NEED to bridge back to Ethereum, here's an in-depth guide:

Base chain is basically a 1-1 fork of Optimism which means we can leverage all the features that OP has.

This includes a native withdrawal process which allows you to move ETH from Base back to mainnet. The downside is that it takes 7 days due to the challenge period.

Why the 7 day period? Because optimistic rollups need a long enough period to challenge potentially fraudulent claims.

Due to the 7 day period, most people will use 3rd party bridges to bridge back to mainnet quicker. However, the native withdrawal method should always work.

Before going further, please note that the second half of this guide requires that you have git and golang installed on your computer to run a script for withdrawing.

If you do not have either of these, I recommend waiting for Coinbase to release their official bridge frontend.

To start, you'll want to visit the L2StandardBridge contract here: .

Go to the contract section and click on "Write as Proxy"basescan.org/address/0x4200…

Go down to either "withdraw" or "withdrawTo". The only difference between the 2 is that the latter allows you to choose the destination address that receives the ETH on mainnet.

Here's how you should fill out the fields:

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

2) _l2Token - use the value 0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000. This the ETH token address on Base.

3) _amount - this should be the same value you used for part 1, but converted to wei. You can use this to convert:

4) _minGasLimit - put 0

5) _extraData - put 0x

Submit the txn and save the txn hash. We'll refer to it later.eth-converter.com

Before I explain the next step, let's talk a bit about how OP handles withdrawals. Post-Bedrock upgrade, users need to do 2 things before they can withdraw. They first need to post a proof to L1 that they did a withdrawal on the L2 (Base in this case).

After this, the user must wait 7 days to pass so any external party has the opportunity to challenge the proof. If no challenge happens, the user can finalize their withdrawal on L1.

On OP mainnet there's a nice UI to facilitate this, for Base we're going to use a cmd line tool.

Here's the command line tool for withdrawals written by the Base team: (h/t @steveklbnf). Clone the repo locally and run "go install" in the folder. You should be able to run the withdrawer command.github.com/base-org/withd…

The README explains what needs to be done, but you'll essentially run the withdrawer command with the necessary inputs - txn hash from above, rpc url (you can use Alchemy/Infura), and the private key of the account that withdrew (DO NOT SHARE THIS ANYWHERE).

After running this command you'll get a txn hash. You can confirm that your proof went through by looking up this txn hash on Etherscan (for mainnet).

You'll then have to wait 7 days before proceeding. Once this challenge period is over, you can run the second command in the README for finalizing the withdrawal.

There's a good chance the official UI comes out before then which will make this process easier.

The OP stack was always built with a way to bridge back from L2 to L1, they just happened to make a UI to make this process easier.

This guide works for all OP-stack chains.

For a full explanation of the withdrawal process, read more here: community.optimism.io/docs/protocol/…

That's all there is to it - withdrawing isn't particularly hard, but it does require some technical savviness for now.

This guide was made for people that absolutely need to bridge back right now and don't want to wait for the official bridge UI to come out.

Do I recommend you do this? Probably not. A friendly UI is much simpler and less confusing to people.

However, the OP stack was built with a way to trustlessly rage quit funds back to mainnet, and I think it's important that people are aware of this.