Major Ethereum testnets go live as Fusaka upgrade approaches
Ethereum developers released a major testnet rollout in preparation for the Fusaka upgrade, tentatively scheduled for mainnet launch on December 3, 2025.
Fusaka will activate on the Holesky testnet on October 1, the Sepolia on October 14, and the Hoodi on October 28, before the full mainnet deployment. The upgrade targets improvements in throughput, scalability, and data availability.
Core developers outlined the testnet schedule during the ACDC #165 call. The Fusaka upgrade will implement Peer Data Availability Sampling (PeerDAS), raise the block gas limit to 150 million units from 30 million, and introduce Verkle trees for improved proof sizes and storage efficiency.
Holesky, Ethereum's largest testnet, will shut down two weeks after Fusaka's completion. The testnet has experienced technical limitations and large exit backlogs, prompting the Ethereum community to migrate testing operations to Hoodi and Sepolia networks.
Core developers outlined the testnet schedule during the ACDC #165 call. The Fusaka upgrade will implement Peer Data Availability Sampling (PeerDAS), raise the block gas limit to 150 million units from 30 million, and introduce Verkle trees for improved proof sizes and storage efficiency.
Holesky, Ethereum's largest testnet, will shut down two weeks after Fusaka's completion. The testnet has experienced technical limitations and large exit backlogs, prompting the Ethereum community to migrate testing operations to Hoodi and Sepolia networks.
Developers plan to double blob capacity within two weeks after Fusaka activation, supporting rollups with higher data throughput. The capacity increase aims to improve performance for Layer 2 scaling solutions that depend on Ethereum's data availability.
PeerDAS will allow validators to sample small portions of blob data rather than downloading complete datasets. This reduces bandwidth requirements while maintaining network security. Verkle trees replace current Merkle tree structures to reduce proof sizes and improve storage efficiency.
The gas limit increase from 30 million to 150 million units per block represents a five-fold expansion over current transaction processing capacity. This change requires careful coordination across the network to prevent stability issues.
Holesky has served as Ethereum's primary testnet since 2023 but accumulated technical limitations over time. Its retirement reflects Ethereum's shift toward more stable testnet infrastructure. Sepolia and Hoodi will handle future testing requirements.
The Fusaka upgrade follows the Pectra upgrade, which introduced validator efficiency improvements and cost reductions. The testnet rollout allows developers to identify potential issues before mainnet deployment.
Each testnet activation will test different aspects of the upgrade functionality. Holesky focuses on large-scale validator behavior, Sepolia tests smart contract compatibility, and Hoodi validates rollup integration.
The December 3 mainnet date remains tentative pending successful testnet completions. Developers may adjust the timeline based on testnet results and any issues discovered during the rollout phase.
PeerDAS will allow validators to sample small portions of blob data rather than downloading complete datasets. This reduces bandwidth requirements while maintaining network security. Verkle trees replace current Merkle tree structures to reduce proof sizes and improve storage efficiency.
The gas limit increase from 30 million to 150 million units per block represents a five-fold expansion over current transaction processing capacity. This change requires careful coordination across the network to prevent stability issues.
Holesky has served as Ethereum's primary testnet since 2023 but accumulated technical limitations over time. Its retirement reflects Ethereum's shift toward more stable testnet infrastructure. Sepolia and Hoodi will handle future testing requirements.
The Fusaka upgrade follows the Pectra upgrade, which introduced validator efficiency improvements and cost reductions. The testnet rollout allows developers to identify potential issues before mainnet deployment.
Each testnet activation will test different aspects of the upgrade functionality. Holesky focuses on large-scale validator behavior, Sepolia tests smart contract compatibility, and Hoodi validates rollup integration.
The December 3 mainnet date remains tentative pending successful testnet completions. Developers may adjust the timeline based on testnet results and any issues discovered during the rollout phase.
Author
Sebile Fane cut her teeth in blockchain by building tiny NFT experiments with friends in her living room, long before the buzzwords took hold. She’s driven by a curiosity for the human stories behind smart contracts — whether it’s a small-town artist minting her first token or a DAO voting on climate grants — and weaves technical insight with genuine empathy.
