The Altair beacon chain upgrade is ready to be activated on the Ethereum mainnet. The upgrade will go live at epoch 74240 (Oct 27, 2021, 10:56:23am UTC).

Client Versions

In order to be compatible with the Altair upgrade, beacon node operators must update the client version that they run. If you run a validator, you must upgrade to continue to follow the mainnet beacon chain. Failure to do so will result in downtime penalties.

The versions listed below are support the mainnet Altair upgrade.

EDIT: The following table has been edited to reference the latest Altair client releases prior to the mainnet upgrade. These contain security patches and optimizations so we recommend *all users upgrade to the latest versions.*

Client Version Number Release Link
Lighthouse v2.0.1* Release
Lodestar v0.31.0 Release
Nimbus v1.5.2* Release
Prysm v2.0.2* Release
Teku 21.10.1* Release

* Client releases referenced with an asterisk have been changed since the original announcement.

Upgrade for Validators

Although this upgrade has been extensively tested if you are a validator on Mainnet, we strongly recommend being online during the time of the upgrade in the event that any unforseen issues emerge.

Bug Bounty Bonus

In order to get more eyes on the Altair upgrade, all bounties for vulnerabilities related to the Altair upgrade have been doubled between now and four weeks after the launch (Nov 27). Critical Altair bugs in both clients and specs are now worth up to $100k.

See the bug bounty program for more details.

FAQ

As an Ethereum user or Ether holder, is there anything I need to do?

This upgrade is purely for the beacon chain consensus mechanism and does not affect end-user accounts, contracts, and state secured by the proof-of-work chain.

If you run your own beacon node, you need to upgrade your node. See the “As a non-validator beacon node operator, what do I need to do?”” section below.

As a non-validator beacon node operator, what do I need to do?

Download the latest version of your beacon node client, as listed in the table above.

As a validator, what do I need to do?

Download the latest version of the software you run, as listed in the table above. Follow any instructions in the release and restart your node with your standard restart procedure.

Note, node software that supports independent validator clients will require an upgrade and restart to this component as well. Please read warnings and instructions contained in the official releases.

What happens if I am a validator or node operator and I do not participate in the upgrade?

If you are using a beacon node client that is not updated to the latest version (listed above), your client will sync to the pre-fork beacon chain once the upgrade occurs. You will be stuck on an incompatible chain following the old rules.

If you run a validator, the validator will be unable to participate in the upgraded consensus and will continue to operate on the post-upgrade beacon chain network. This will result in penalties with respect to the upgraded Mainnet chain.

What happens during a beacon chain network upgrade?

After the Ethereum community comes to an agreement concerning which changes should be included in the upgrade, changes to the protocol are written into the various clients. The beacon chain protocol changes are activated at a specific epoch number. Any nodes that have not been upgraded to the new ruleset will be abandoned on the old chain where the previous rules may continue to exist.

Why “Altair”?

After community discussion and emoji voting, client teams decided to use star names for each upgrade where the sequence of upgrade names are in alphabetical order.

Altair starts with a “A”, is the twelfth brightest star in the night sky, rotates quite rapidly with an equatorial velocity of 286 km/s, and is the location of the Forbidden Planet. Pretty cool star if you ask us.

Thank you!

Huge shoutout to all of the researchers, engineers, and community members that have put an incredible amount of work into this first beacon chain network upgrade.

Now, onward to the Merge 🚀

Disclaimer

This is an emergent and evolving highly technical space. If you choose to implement the recommendations in this post and continue to participate, you should make sure you understand how it impacts you. You should understand that there are risks involved including but not limited to risks like unexpected bugs. By choosing to implement these recommendations, you alone assume the risks of the consequences. This post and recommendations are not a sale of any kind, and do not create any warranties of any kind including but not limited to anything related to the Ethereum network, or the Ethereum clients referred to herein.