Fusaka upgrade is expected to increase Ethereum's data capacity by 8 times, while enhancing DoS defense capabilities and introducing new developer tools.
Written by: Jason Nelson
Translated by: Luffy, Foresight News
Abstract
Ethereum will undergo the Fusaka upgrade in December 2025, which will bring data expansion, DoS defense, and developer tools.
Peer Data Availability Sampling (PeerDAS) increases the throughput of data blocks (blobs) by 8 times through "sampling data instead of storing complete data on full nodes."
New EIPs will set blob fees, limit block sizes, and introduce features such as pre-confirmation and P-256 signature support.
The next major upgrade of the Ethereum network is on the horizon. This upgrade, named Fusaka (an abbreviation of Fulu-Osaka), is scheduled to go live in December 2025 and will make significant adjustments to both the execution layer and the consensus layer of Ethereum.
The Fusaka upgrade is another milestone following Ethereum's merge in 2022. The Shapella upgrade in 2023 introduced staking ETH withdrawals; the Dencun upgrade in 2024 introduced prototype Danksharding technology and blobs; and the Pectra upgrade in 2025 will enhance validator flexibility and Layer 2 interoperability.
According to the roadmap, the Fusaka upgrade aims to expand data capacity, strengthen defenses against DoS attacks, and introduce new tools for developers and users.
This upgrade has far-reaching implications. Fusaka is not a minor patch but a redesign of Ethereum's data availability management, blob pricing, and transaction protection mechanisms. Its success will depend on whether Ethereum can scale to meet the growing demands of Layer 2 networks without causing network splits or overburdening node operators.
PeerDAS: Sampling Instead of Storing All Data
The core feature of the Fusaka upgrade is PeerDAS, a new way to handle blobs.
In Ethereum, blobs are temporary data packets introduced with the prototype Danksharding technology in the Dencun upgrade. They allow Rollups to submit large amounts of transaction data to the mainnet at a low cost, thereby improving scalability without permanently increasing the blockchain state.
This ensures redundancy, but as demand grows, it can also create bottlenecks. Under the current model, every full node in Ethereum must store all Layer 2 network blobs submitted to the chain.
PeerDAS changes this logic. Each node only needs to store a portion of the blob (about one-eighth) and relies on cryptographic reconstruction techniques to fill in the missing data fragments. This design verifies data availability through random sampling, with an error probability as low as 1 in 10²⁰ to 10²⁴.
With this distributed storage approach, Ethereum can theoretically increase blob throughput by 8 times without requiring node operators to upgrade their hardware or bandwidth. Rollups that rely on blobs to publish compressed transaction data are expected to be the most direct beneficiaries.
The Economics and Flexibility of Blobs
The Fusaka upgrade also reshapes the pricing and management mechanisms for blobs.
A key adjustment is EIP-7918, which introduces a minimum reserve fee for blobs. Under the current rules, when execution layer gas fees dominate, blob prices can drop to near zero, leading to inefficient usage. The minimum reserve fee ensures that there is always a baseline cost for blob usage, forcing Layer 2 to pay for the storage and bandwidth they consume.
Another mechanism is EIP-7892, which introduces a fork that only adjusts blob parameters. This allows Ethereum clients to adjust blob throughput without a complete hard fork, enabling developers to respond flexibly to unpredictable Layer 2 demands without waiting for the next scheduled upgrade.
Strengthening Attack Defenses
Scaling also means that Ethereum's attack surface expands. The Fusaka upgrade includes a series of adjustments to limit extreme scenarios and protect the network from DoS attacks:
EIP-7823: Limits the input size of the MODEXP operation to 8192 bits;
EIP-7825: Sets a gas limit of 2²⁴ units per transaction;
EIP-7883: Increases the gas cost for large exponents in MODEXP to better match computational workload.
EIP-7934: Limits the execution layer block size to 10MB.
These adjustments collectively reduce the risk of extreme transactions or oversized blocks causing client overload, propagation stalls, or network instability.
New Tools for Users and Developers
The Fusaka upgrade also aims to enhance usability.
For users, EIP-7917 introduces pre-confirmation support. This allows wallets and applications to preview the validator proposal schedule, enabling users to lock in the certainty that their transactions will be included in subsequent blocks, thereby reducing latency and uncertainty in transaction confirmations.
For developers, the Fusaka upgrade introduces two important features:
CLZ opcode, suitable for cryptographic algorithms and contract optimization;
EIP-7951, providing native secp256r1 (P-256) signature verification. This is a commonly used elliptic curve in hardware devices and mobile systems, and its inclusion will enhance compatibility and account abstraction capabilities.
These adjustments aim to lower the barriers for application developers, paving the way for new wallet designs and security models.
What ETH Holders Need to Know
For ordinary Ethereum users, no action is required for the Fusaka upgrade. Account balances, tokens, and applications will continue to operate as usual. The official Ethereum website emphasizes that users should be wary of scams requesting ETH upgrades or transfers, as the upgrade does not require such actions.
The responsibility primarily falls on validators and node operators, who must synchronize the upgrade of both the execution layer and consensus layer clients. Coordination is crucial: if validators do not synchronize, the network may face downtime or temporary fork risks.
Following a series of successful testnet activations, the Fusaka upgrade is scheduled to launch on the Ethereum mainnet on December 3, 2025.
The Future of Ethereum After the Fusaka Upgrade
The Fusaka upgrade is one of the boldest moves in Ethereum's roadmap since the merge. It attempts to achieve three major goals simultaneously: increasing blob capacity, strengthening defenses, and updating developer tools through a coordinated release.
Testing and development are ongoing, with client teams focusing on PeerDAS performance, blob pricing models, and the compatibility of execution layer and consensus layer software. If the upgrade is successful, Fusaka is expected to become a turning point for Ethereum in responding to the next wave of Layer 2 network adoption and enhancing scalability.
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