After months of anticipation and behind-the-scenes development, Ethereum core contributors have finally set a date for the Fusaka upgrade.
Summary
- Ethereum’s Fusaka upgrade has been scheduled for Dec 3, 2025.
- Testnet upgrades on Holesky, Sepolia, and Hoodi will take place in October before the main rollout.
- The upgrade introduces major scalability changes, aimed at making the network more efficient.
- Two follow-on Blob Parameter Only upgrades will gradually raise blob capacity from 6 to 15, then 21 blobs per block, boosting data throughput for rollups.
Ethereum developers have officially confirmed that the Fusaka upgrade, the next major network update, will roll out on December 3, 2025. The announcement was made during the latest AllCoreDevs meeting, pushing the release back from the originally scheduled November timeline.
Fusaka is aimed at scaling Ethereum, particularly by improving data availability for Layer 2 (L2) networks, making the network faster and cheaper. Unlike previous forks like Pectra, which introduced visible user-facing features, Fusaka focuses on optimizations, bundling 11 Ethereum Improvement Proposals (EIPs) to enhance core protocol functionality.
Ethereum researcher Christine D. Kim confirmed that testnet upgrades on Holesky, Sepolia, and Hoodi will occur in October to prepare the network for Fusaka, with exact timing to be unveiled in the coming days.
To support the rollout, developers also scheduled two “blob parameter only” (BPO) upgrades to follow Fusaka. These BPO upgrades will lift the maximum number of “blobs,” special data packets that rollups use to store and share information cheaply, from the current 6 to 15 blobs per block in the first step and 21 blobs per block in the second.
The extra lead time will help catch any consensus bugs, allow node operators to upgrade without pressure, and ensure smooth coordination among execution and consensus clients. Unless unexpected issues emerge during the test period, Fusaka is now set to land on mainnet with the blob-capacity increases following close behind.
Reinforcing the focus on security, the Ethereum Foundation has launched a four-week audit contest with up to $2 million in bug-bounty rewards. The program invites independent researchers to probe Fusaka’s code for vulnerabilities ahead of the December mainnet rollout.
Ethereum Fusaka upgrade: What to expect
Fusaka is designed around strengthening the Ethereum network’s foundations. At the heart of the upgrade is a new technique called PeerDAS (Peer Data Availability Sampling), which will boost Ethereum’s resource efficiency, data capacity, and scalability.
While Fusaka will not immediately change smart contract behavior, its real impact lies in laying the groundwork for Ethereum to reach up to 12,000 transactions per second by 2026, a leap that could redefine the blockchain’s role in powering rollups, DeFi, and gaming.
The upgrade will also reduce gas fees for L2 projects, making Ethereum cheaper and faster to use. This could make the network more appealing for DeFi platforms, on-chain games, and real-world asset protocols, all of which rely on scalable infrastructure and cost-efficiency.
To keep the network stable under the added load, Fusaka also introduces stronger spam-prevention rules. These changes make it costlier to flood Ethereum with low-value transactions while keeping normal user costs steady. On top of that, the upgrade makes stored data more efficient and lays the groundwork for future improvements.
With the countdown now officially underway, all eyes will be on the October testnets and the December mainnet deployment as Ethereum marches toward a more scalable future.
