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Ethereum's Fusaka Upgrade Set for December 3, Poised to Double Blob Capacity

By ToTo BugelmanNewcomer0 rep· 9/19/2025
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Ethereum's core developers have confirmed that the highly anticipated Fusaka upgrade is slated for a mainnet launch on December 3. This significant network enhancement aims to bolster scalability and efficiency, primarily by doubling the capacity for "blobs," which are crucial for storing large datasets off-chain and improving the performance of Layer-2 networks.

 

Christine D. Kim

 

Key Takeaways

  • The Fusaka upgrade is scheduled for mainnet activation on December 3.

  • Blob capacity will be doubled through a phased approach with two "Blob-Parameter Only" (BPO) forks.

  • The upgrade focuses on backend improvements, enhancing scalability and node efficiency without introducing new user-facing features.

  • A rigorous testnet rollout will precede the mainnet launch, starting with Holesky on October 1.

 

Fusaka Upgrade Details

The Fusaka upgrade is designed to enhance Ethereum's infrastructure, focusing on scalability and efficiency. A key component is the introduction of Peer Data Availability Sampling (PeerDAS), which allows validator nodes to verify large datasets, known as blobs, by sampling smaller portions from peers rather than downloading entire datasets. This is expected to reduce bandwidth and storage requirements, thereby improving Layer-2 rollup scalability.

The upgrade also includes proposals to increase the block gas limit, potentially enabling higher transaction throughput. Furthermore, it incorporates Verkle Trees for optimized data storage and improvements to EVM performance for faster smart contract execution. The upgrade will activate approximately a dozen Ethereum Improvement Proposals (EIPs) that target these core areas.

 

Phased Blob Capacity Expansion

A significant aspect of the Fusaka upgrade is the planned doubling of blob capacity. This will be achieved through a series of "Blob-Parameter Only" (BPO) forks. The first BPO fork is scheduled to occur approximately two weeks after the mainnet launch, increasing the target/max blob count from the current 6/9 to 10/15. A second BPO fork will follow on January 7, 2026, further expanding the capacity to 14/21 blobs per block. These BPO forks are designed to adjust protocol parameters without requiring client software updates, ensuring a smooth transition for users and applications.

 

Testnet Rollout and Security

Prior to the mainnet deployment, Fusaka will undergo a comprehensive testing phase across three public testnets: Holesky, Sepolia, and Hoodi. The rollout begins with Holesky on October 1, followed by Sepolia on October 14, and Hoodi on October 28. Each testnet will execute the complete sequence of Fusaka upgrades, including the BPO forks, to thoroughly validate the blob capacity expansion mechanisms and identify any potential issues. The Ethereum Foundation has also launched a four-week code audit program, offering up to $2 million in rewards for developers who discover and disclose vulnerabilities in the Fusaka codebase, underscoring a commitment to network security.

 

Barnabas Busa

 

Impact on Scalability and Future Roadmap

The Fusaka upgrade is expected to significantly alleviate scalability pressures on the Ethereum network, particularly benefiting Layer-2 solutions by reducing transaction costs. This move complements broader scalability efforts and sets the stage for future developments, including potential further increases in gas limits and enhancements to the Layer-2 ecosystem. The upgrade aims to support Ethereum's evolution towards seamless cross-chain interoperability while maintaining its core principles of decentralization and security.

 

Sources


This article was created with support from AI-driven technology, drawing on multiple reputable sources. The final content has been thoroughly reviewed and edited by BlockzHub's editorial team to ensure accuracy, clarity, and coherence. Original reporting sources are credited whenever appropriate and as required. The opinions expressed in this article do not necessarily represent the official views or positions of BlockzHub. This article is intended for informational purposes only and should not be considered financial or professional advice. Investing involves risk, and you should consult a qualified financial advisor before making any investment decisions.

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