Continued Path to Decentralization: Bridging Tokens into Arbitrum

Offchain Labs
3 min readSep 10, 2021


Before diving into the next steps on our roadmap, we just want to give a quick shoutout to the whole community! It has been an incredible ten days (yes, it’s only been 10 days!) and we are thrilled to be sharing this moment with all of you. This is a huge step in the Ethereum community’s migration from L1 to L2 and we could not be more excited by the progress so far!

As noted in our post last week, we have opened the system to all users for arbitrary contract deployment and any other interactions, but we are currently, as of writing, maintaining a whitelist on which tokens can be bridged into Arbitrum as we coordinate with projects on this matter.

The reason for this is to help ensure that projects get the type of token that suits their needs: when bridged over to Arbitrum, a token can have one of two types of contracts on L2: a Standard ERC-20 token, which supports basic ERC-20 functionality along with affordances to transfer between L1 and L2, or a Custom ERC-20, which can be deployed with any other functionality (governance, snapshotting, etc). If a Standard ERC-20 would be bridged across and the project later chooses to create a Custom ERC-20 implementation, we wind up with two different L2 representations of the same token. While this isn’t a security risk (i.e., users’ funds wouldn’t be lost / users would still maintain the ability to withdraw their funds to L1), it introduces usability complexities and inconveniences we’d like to do our best to avoid — having multiple representations of the same token on Arbitrum One that are not fungible.

That being said, we do not want to maintain this whitelist for much longer and would love for permissionless token bridging to be available as soon as possible. To balance these countervailing considerations, we have come up with an approach that we have designed but are open to iterate based on strong community feedback. Our plan is to maintain the whitelist for the next six weeks (until October 22nd) at which point we will be opening it up and the default bridging for any assets that have not been bridged will be a Standard ERC-20. We expect that this additional six week period (on top of the months we already spent communicating with projects during our developer-mainnet phase) will be sufficient time for projects to determine if they need custom functionality and implement all necessary actions as well, but again, we are open to community feedback.

When determining whether a project requires a custom implementation, it is important to consider whether maintaining things like governance or snapshotting on Arbitrum are important. Be aware that your Standard ERC-20 contract will not be upgradeable and migrating a token from a standard ERC-20 to a token with additional affordances can be an extremely complex social coordination process at a later stage, and it may make sense to coordinate prior to having the token go live on Arbitrum.

So spread the word: if your token needs a custom contract on Arbitrum, the time to set it up is before October 22nd! You can check out our documentation on registering a custom token here and on a Standard ERC-20 here; we also highly recommend that you contact us directly, which you can do via this form.

Again, if your token requires a standard implementation on Arbitrum, you will be able to permissionlessly deploy it via our bridge on October 22nd if, however, you really, really don’t want to wait that long, you can contract us via the same form, and we can whitelist it for you before then.

There are many projects that we are aware of that are currently still working on finishing their custom token implementations, which required us to consider maintaining the whitelist on token-bridging, or hold off on opening mainnet (which nobody would have wanted!!). We strongly believe that the short-term friction of this process will be extremely beneficial in the long run as many functionalities like governance move into rollups over time. We are so excited to be working with all of you and look forward to bridging your tokens into Arbitrum One. We’ll be posting more about our decentralization roadmap soon!