What is Ethereum Altair Upgrade?

Ethereum Altair upgrade arrived on October 27, 2021 on the Ethereum 2.0 mainnet. Why was it so anticipated and what does it mean, explained in our new recap.

Key Takeaways

  • The Ethereum Altair upgrade is the first planned update to the Ethereum beacon chain (Ethereum 2.0). It was launched on Oct 27, 2021 at 10:56:23 UTC and introduced some changes to consensus and rewards and punishment;
  • The hard fork will require action from node operators and validators and will not affect end-users of Ethereum beacon chain;
  • The Ethereum community anticipates that this update will serve as a stepping stone for the merger of legacy Ethereum chain and Ethereum 2.0 and usher in the transfer to Proof-of-Stake.

What is Ethereum Altair Upgrade?

Proof-of-Work Ethereum chain has had eleven upgrades so far, with the London hard fork being the latest. However, this has not been the case with the Proof-of-Stake Ethereum chain until recently.

Altair is the first scheduled update to the beacon chain of Ethereum (commonly known as Ethereum 2.0). It was performed as a hard fork, meaning once it is active, there is a new chain with new rules and old chain, which will die out.

When Will the Ethereum Altair Upgrade Happen?

According to the official blog post, Ethereum Altair upgrade will take effect in epoch 74240. In more common terms, this block activated on Oct 27, 2021 at 10:56:23 UTC.

When will ETH 2.0 launch and Ethereum 2.0 merge with the main network? While this planned upgrade to the beacon chain warms up the merger development, exact dates of arrival are still up in the air. Optimistic estimates put the date of launch sometime in 2022.

What Will Change?

Ethereum Altair upgrade will bring several new features and rules to the Ethereum 2.0 chain.

  • Light clients (abridged copies of the blockchain) will be able to participate in core consensus;
  • Fixed bugs and cleaned up incentive accounting (i.e. rewards calculation);
  • More strict slashing parameters (for stakers that do not participate and validate properly). This can be crucial for the security of the network, incentivizing all nodes to work properly.

As can be inferred from the list of changes, they will only affect validators and node operators.

What should an ETH holder do for the Altair upgrade? Ethereum holders and users do not need to do anything. Node operators and validators must upgrade until the deadline to keep working in the live version of Ethereum 2.0.

How will ETH staking work after the Altair upgrade? The hard fork does not change staking fundamentally, so aside from some changes in calculations of rewards and punishments, nothing changes much in Ethereum staking for now. Altair does not make withdrawals of ETH stakes possible yet, so validators will have to wait until the merge.

Tweets on Ethereum Altair Upgrade

While we were preparing this guide, Altair went live! The community is celebrating this milestone and is already looking forward to the next update.

News outlet Crypto Amb made an article raising and debunking concerns about the Altair upgrade. The only impactful fact is that 17% of the nodes remained in the old chain and might suffer the consequences.

User MinusWells explained why Altair upgrade is so vital to the merger of Ethereum networks and transition to Proof-of-Stake.


Community members have already dubbed Ethereum Altair upgrade a “low stakes warm-up” for the merger with Ethereum 2.0. Since the current iteration of beacon chain represents how Ethereum will work in the future, it is vital to have at least one dress rehearsal.

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4 months ago

I doubt what 2.0 will do.