Ethereum is set to undergo a significant upgrade, "Fusaka," on December 3, 2025, at 21:49:11 UTC, marking a pivotal moment in its ongoing quest for enhanced scalability and efficiency. This upgrade follows the "Pectra" upgrade in May 2025 and represents a strategic advancement in how the network handles data, particularly concerning Layer 2 rollups.
"Fusaka," a blend of the code names "Osaka" (execution layer upgrades) and "Fulu" (consensus layer upgrades), underscores Ethereum's dedication to both technical improvements and community involvement. The upgrade introduces 12 Ethereum Improvement Proposals (EIPs) aimed at enhancing data availability, Layer 1 performance, security, and network optimization.
At the heart of Fusaka lies Peer Data Availability Sampling (PeerDAS), a solution designed to revolutionize how Ethereum handles data from rollups. Rollups, such as Arbitrum, Optimism, and zkSync, bundle thousands of transactions and post summaries to Ethereum for security, effectively scaling the network. However, they are constrained by the cost and amount of data posted back to Layer 1. PeerDAS addresses these limitations by allowing validators to verify rollup data blocks without downloading the entire block. Instead, the data is split into smaller units, and validating nodes acquire only random fragments, reducing bandwidth and storage needs. This approach paves the way for an increase in blob capacity without requiring stakers to upgrade hardware. It is estimated that PeerDAS can reduce bandwidth requirements by up to 85%.
In addition to PeerDAS, Fusaka introduces a "Blob-Only Parameter" (BPO) fork, new gas and block size limits, and adjustments to historical expiry. The upgrade will increase the block gas limit to 60 million, a significant rise from the previous limit of approximately 36 million. To safely increase the block gas limit, the upgrade introduces a cap on any single transaction at 16,777,216 gas. These changes enable the blockchain to adapt to multiple capacity increases and allow more transactions and computations to fit into each block, reducing mainnet gas fee spikes. The rollout of these features is carefully scheduled to ensure network stability, with mainnet activation on December 3, 2025, followed by BPO1 on December 9, 2025, and BPO2 on January 7, 2026.
Fusaka is projected to significantly impact Layer 2 transaction costs, with estimations of a 40-60% reduction as rollups benefit from increased data availability space. This upgrade enables true Layer 2 scaling, providing 3.5 times more space to post transaction data. Moreover, Fusaka expands Ethereum's data capacity, enabling over 100,000 transactions per second (TPS) through Layer 2 rollups while keeping node requirements manageable.
Looking ahead, the next major upgrade after Fusaka is "Glamsterdam," targeted for 2026. Building on the improvements introduced by Fusaka, Glamsterdam aims to further increase throughput while maintaining decentralization and validator accessibility.
In conclusion, the Fusaka upgrade represents a crucial step forward in Ethereum's evolution, enhancing its scalability, efficiency, and overall user experience without compromising its core principles. By strategically addressing data availability and optimizing network parameters, Fusaka paves the way for a more robust and scalable Ethereum ecosystem, capable of supporting a growing number of users and applications.
