Wen Arbitrum?

Offchain Labs
Offchain Labs
Published in
3 min readMay 12, 2021


tl;dr: We’ve added Sequencer support and will open an Arbitrum Sequencer testnet on May 14. We plan to open Arbitrum mainnet to developers on May 28.

Yes, we hear you! Loud and clear! Gas fees are high and Ethereum users need relief. We’ve been hard at work getting Arbitrum ready for prime time, and we know the community is ready, so…(drum roll)… we have some exciting updates!

Technical update: now with 100% more sequencer

First, a technical update. When we previously announced our release candidate testnet, Arbitrum did not include a Sequencer. What this meant was transactions did not get “instant responses” and had the same latency as Ethereum. Our goal had been to launch our initial mainnet without a sequencer and add a sequencer later via an upgrade, but based on feedback from our amazing beta-testers, we went ahead and added Sequencer support now ahead of our launch!

It took us a few extra weeks to get here (sorry! 😬), but we think it was well worth it as the user experience has gone wayyyy up and response times have gone wayyyy down 😎! Notably, while we expect most users to use the Sequencer, users now have the choice to post their transactions via the Sequencer or directly on-chain. We’ll launch a new testnet with the Sequencer on May 14.

Fair Launch

We have two important principles guiding our launch

  • Arbitrum is a community project, and open to everyone. We welcome all projects and users, and won’t be picking winners or giving specific projects priority access.
  • We want to make sure Arbitrum has an active and vibrant ecosystem for users as soon as it’s available to them.

To facilitate a fair launch and a robust ecosystem from inception, we will be opening Arbitrum for developers first, so that projects joining the initial cohort have time to set up the infrastructure and test. We’ll be giving access to any projects that want it, and will open up to end-users shortly thereafter, once a quorum of projects are up and running. We’ll work with the projects to make sure they’re ready, but we don’t expect it to be long.


We will open up Arbitrum Ethereum mainnet for developers on May 28. That’s in 16 days 👀! To prepare for that, we’ll launch a Sequencer testnet on May 14.

Who’s joining the party?

Great question! Over the next few weeks leading up to our mainnet release we’ll be doing a series of announcements and have amazing projects joining us — both infrastructure and dapps!

Can I get access?

Yes! It’s a fair launch, and everybody is invited. If you’re a developer, fill out this form for access to the developer mainnet!

A word of caution

We’re doing our absolute best to get Arbitrum out on Ethereum mainnet for you to use, and sharing dates so that you can prepare accordingly. The dates in this post are based on the best information currently available to us, but considering the magnitude of the project, there is always the possibility that things shift.

Let’s get those gas fees down and scale Ethereum 🚀



Offchain Labs
Offchain Labs

We’re Building Arbitrum, a scaling solution for Ethereum. Learn more at https://offchainlabs.com/ and http://arbitrum.io/.