Ethereum core developers have confirmed December 3, 2025, as the launch date for its next major upgrade, Fusaka. This announcement was made during the All Core Developers Consensus call (ACDC 165) on September 18, signaling a crucial advancement in Ethereum’s scaling roadmap.
The upgrade will first be implemented across three test networks throughout October, serving as a prelude to its launch on the main Ethereum network. This phased testing approach is designed to identify and resolve any potential issues, ensuring that millions of users and substantial financial transactions can rely on the updated code.
Testing Phase Initiatives
The testing for Fusaka will begin with the Holesky testnet on October 1, followed by Sepolia on October 14, and Hoodi on October 28. This preparatory period is essential for developers to catch problems without endangering real assets or disrupting live applications. Each testnet will function as a checkpoint, allowing teams to validate that the new features are functioning as expected before advancing to the main network.
Developers are in the process of finalizing exact epoch numbers and timing details. The code was frozen on September 22, providing the validation team ample time to conduct thorough inspections. Subsequent client releases are scheduled for September 25, enabling node operators to adequately prepare their systems for the upgrade.
Innovative Features of Fusaka
Fusaka is expected to introduce 11 to 12 technical enhancements aimed at increasing Ethereum’s speed and cost-effectiveness. One of the key features, PeerDAS (Peer Data Availability Sampling), will allow network validators to verify transaction data more efficiently. This method is likened to quality control in manufacturing, where random samples are checked to ensure overall standards without having to inspect every single unit, thus conserving storage and bandwidth while enhancing network security.
In addition, the upgrade will increase the size limit for smart contracts from 24KB to 48KB, providing developers with more space to devise complex applications without fragmenting their code.
Capacity Expansions
Shortly after Fusaka’s implementation, developers plan to activate the first of several “Blob Parameter Only” updates, significantly boosting the amount of data the network can process. Currently, Ethereum can handle 6 to 9 “blobs” of data per block; the first of these updates will lift that total to between 10 and 15 blobs, and another increase is anticipated shortly after. By around January 7, 2026, further enhancements could more than double the blob capacity.
These blobs play a vital role for Layer 2 networks like Arbitrum and Optimism, which have proven to enhance transaction speed and reduce costs. Following the Dencun upgrade in March 2024, these Layer 2 solutions experienced marked reductions in monthly operational costs. The anticipated improvements from Fusaka are expected to further lower costs while increasing transaction capacity, potentially allowing Ethereum to process up to 12,000 transactions per second by 2026.
Focus on Security and Stability
To fortify the integrity of the upgrade, the Ethereum Foundation has initiated a four-week security audit, offering up to $2 million in rewards to researchers who successfully identify vulnerabilities. This bug bounty program will continue until the December launch, granting security experts ample opportunity to examine the code. Current evaluations have reported promising results, with early testing networks demonstrating over 96% validator participation with few minor issues.
Fusaka will also introduce enhanced anti-spam measures, aimed at preventing misuse of the network through junk transactions while keeping normal usage costs stable. Existing applications and wallets will retain compatibility, with most users needing no action. However, validators and node operators will be required to update their software ahead of each network upgrade to avoid penalties.
Strategic Timing and Anticipated Market Impact
The timing of Fusaka’s launch, just seven months after the Pectra upgrade in May, underscores Ethereum’s commitment to accelerated development cycles and positions the network for stronger institutional adoption. The chosen launch date strategically aligns with the upcoming Devconnect conference in Buenos Aires, where Ethereum developers will gather to strategize future enhancements.
Market analysts view Fusaka as a pivotal element in Ethereum’s growth trajectory for 2026. With lower expenses, greater capacity, and improved operational efficiency, the upgrade is anticipated to attract a wider base of developers and users, potentially driving Ethereum toward new price heights.
As a cornerstone for Ethereum’s next growth phase, Fusaka signifies more than just a technical upgrade; it reflects the network’s maturing focus on infrastructure and practical solutions. With testing already yielding strong results and a clear timeline established, Ethereum is poised for its most significant scaling milestone since the Merge in 2022. The December 3 launch not only marks a critical upgrade date but also heralds a potential transformation into a global-scale platform.
