Ethereum’s Fusaka upgrade has been activated on the Sepolia testnet, marking the next major step in the network’s ongoing push to improve scalability and performance.
The upgrade marks the second phase of a three-step rollout under Ethereum’s Fusaka roadmap, following the Holesky testnet activation on Oct. 1. The Sepolia deployment focuses on stress testing the network’s new data-availability system and higher block gas limit before developers push the code to the final Hoodi testnet later this month.
Fusaka’s rollout is introducing a suite of performance and consensus improvements. The full upgrade aims to increase Ethereum’s block gas limit to 60 million, allowing blocks to process more transactions and complex smart-contract activity while testing whether nodes can maintain stability at higher capacity.
“There was solid engineering work by the client teams to ensure that the current node setups, both in terms of hardware and networking, can reliably handle 60M gas blocks without risking networking instability,” Gabriel Trintinalia, protocol engineer at Consensys’ client Besu and a core developer on the upgrade, told Cointelegraph.
Since larger blocks result in nodes processing and storing more data, Peer Data Availability Sampling (PeerDAS) is also being tested.
PeerDAS lets Ethereum validators verify transaction data by sampling small pieces from multiple peers instead of downloading everything, improving speed and scalability while staying decentralized.
Paul Harris, another Fusaka core developer and a protocol engineer at Consensys’ Teku client, said that under PeerDAS, validators no longer need to store all network data, significantly reducing the burden on nodes.
“Fusaka changes how data availability is done, enabling scaling beyond what was possible before PeerDAS,” Harris said.
The Ethereum Foundation unveiled the Fusaka testnet schedule on Sept. 26, outlining the final steps before the network’s next major upgrade. Fusaka follows this year’s Pectra update, with its final trial on the Hoodi testnet set for Oct. 28 and a mainnet launch expected in December.
A brief history of Ethereum upgrades
Since its launch in July 2015, the Ethereum network has undergone several major upgrades to improve scalability, security and performance.
The most recent review took place on May 7, when the Pectra upgrade went live, introducing three key improvement proposals. Among the changes, Pectra enabled externally owned accounts to function like smart contracts and pay gas fees in tokens other than ETH, and raised the validator staking cap to 2,048 ETH from 32 ETH. The upgrade also expanded the number of data blobs allowed per block.
Before Pectra, Ethereum rolled out the Dencun upgrade on March 13, 2024, drastically reducing the cost of gas fees in the network. Within one year of the Dencun upgrade, the average gas fees on Ethereum dropped by as much as 95%.
Perhaps the most famous Ethereum upgrade is known as The Merge, which occurred in September 2022 and transitioned Ethereum to a proof-of-stake blockchain from a proof-of-work blockchain.
The Merge resulted in the end of mining and the introduction of validators, along with a reduction in energy costs by up to 99%.
The Shanghai upgrade in April 2023 was also a critical step for the network’s roadmap, as it allowed validators staking Ether (ETH) to make withdrawals for the first time, and completed Ethereum’s transition to proof-of-stake.