Quick Summary of the Fusaka Upgrade
- The Ethereum network is set to undergo the Fusaka upgrade on December 3, 2025, marking a significant step in its ongoing development.
- Fusaka’s primary goal is to enhance Ethereum’s scalability by improving data availability for layer-2 rollups via PeerDAS technology.
- The upgrade includes adjustments to gas and block size limits, as well as history expiry tweaks, preparing the chain for future capacity increases.
- Beyond scaling, Fusaka introduces improvements to user experience, security, and developer tools, making Ethereum more accessible and efficient.
- The changes brought by Fusaka are expected to benefit layer-2 ecosystems, node operators, validators, and ETH holders, contributing to the overall growth and adoption of Ethereum.
What is the Ethereum Fusaka Upgrade?
Scheduled for activation on December 3, 2025, the Ethereum Fusaka upgrade represents the second major hard fork of the year, following Pectra in May. This upgrade aims to address the growing demand for Ethereum transactions and the associated costs, particularly as rollups become more prevalent.
Rollups, which handle a significant portion of Ethereum’s transactions and fee revenue, face limitations in data posting to the layer 1 and the costs involved. Fusaka seeks to alleviate these constraints through several key features.
The centerpiece of Fusaka is Peer Data Availability Sampling (PeerDAS), allowing validators to verify rollup blob data without downloading the entire dataset. This reduces bandwidth and storage requirements and paves the way for significantly higher data throughput.
✅ PeerDAS is a game-changer because it offloads data verification duties across the network, slashing individual bandwidth needs while ensuring data integrity.
Alongside PeerDAS, Fusaka introduces Blob-Only Parameter (BPO) forks, new gas and block-size limits, and history expiry tweaks, all designed to prepare the Ethereum blockchain for continuous capacity enhancements.
In essence, Fusaka is a multifaceted upgrade that targets scalability, efficiency, and user experience, positioning Ethereum for continued growth and adoption in the years to come.
💡 Keep an eye on the gas fees after the Fusaka upgrade. If the upgrade is successful, you might see lower costs for transactions on layer-2 solutions!
The name Fusaka is a blend of the code names for the Execution Layer (Osaka) and Consensus Layer (Fulu) aspects of the upgrade.
The Roadmap: From Merge to the Fusaka Upgrade
To understand Fusaka’s place in Ethereum’s evolution, it is helpful to consider the upgrades that have preceded it.
- The Merge (2022): Transitioned Ethereum from a proof-of-work to a proof-of-stake consensus mechanism, reducing energy consumption by approximately 99.9%.
- Shapella (2023): Enabled the withdrawal of staked Ether (ETH), creating a liquid staking system and attracting more validators.
- Dencun (March 2024): Introduced Ethereum Improvement Proposal (EIP) 4844 blobs, offering a cheaper, temporary data lane for rollups, also known as protodanksharding.
- Pectra (May 2025): Added EIP-7702 account abstraction features and revised staking parameters, such as the 2,048-ETH validator cap.
These upgrades align with Vitalik Buterin’s roadmap of Merge, Surge, Verge, Purge, and Splurge. The Surge focuses on scaling Ethereum through rollups and improved data availability, while the Verge and Purge aim for lighter clients and pruning old transaction history.
📈 Examining the roadmap helps contextualize the importance of each upgrade. Fusaka is pivotal because it simultaneously pushes the goals of the Surge, Verge, and Purge forward.
Fusaka is unique because it advances all these goals simultaneously. It enhances data scaling for rollups (Surge) and incorporates history expiry and lighter sync mechanisms (Verge and Purge). The upgrade targets a modular Ethereum architecture capable of processing over 100,000 transactions per second (TPS) by combining layer-2 throughput.
Key Changes: PeerDAS, Blobs, and Larger Blocks
The cornerstone of Fusaka’s scaling improvements lies in EIP-7594, known as PeerDAS.
PeerDAS modifies how rollup data blobs are handled. Instead of full nodes downloading entire blobs, PeerDAS divides them into smaller cells and employs sampling and erasure coding. Validators only need to fetch random pieces. The network can confidently verify the existence of complete data if there are enough pieces available.
📍 Think of PeerDAS like checking a few random pages of a book to confirm it’s the right one, rather than reading the whole thing. This saves time and resources while still ensuring accuracy.
This approach reduces bandwidth and storage demands on individual nodes and sets the stage for potentially increasing blob capacity by eightfold without requiring home stakers to use data center hardware.
To facilitate flexible growth, EIP-7892 introduces Blob Parameter Only (BPO) forks, which are small hard forks that adjust three blob-related parameters: target, max, and the base fee adjustment factor.
Following Fusaka, Ethereum can incrementally increase blob capacity in response to layer-2 demand, rather than relying on infrequent, large-scale forks.
✨ BPO forks allow Ethereum to dynamically adapt to changing network conditions, making scaling adjustments more responsive and efficient.
Fusaka also includes updates to gas and block sizing on the execution side:
- The effective block gas target is increased from 45 million to higher levels. EIP-7825 limits the gas used by a single transaction, and EIP-7934 adds a 10 MB Recursive Length Prefix block size limit to mitigate denial-of-service risks.
- EIP-7823 and EIP-7883 reprice and limit the MODEXP precompile to prevent a single cryptographic call from stalling an entire block.
Essentially, Fusaka expands Ethereum’s capacity for rollup data and complex transactions while implementing safeguards to ensure that blocks remain verifiable for standard nodes.
Enhancements to User Experience, Security, and Developer Tools
Fusaka goes beyond increasing raw capacity by incorporating several EIPs that enhance user experience, security, and developer ergonomics.
EIP-7917 (deterministic proposer lookahead) makes the proposer schedule for the upcoming epoch fully deterministic and accessible on-chain via the beacon root. This is crucial for based rollups and pre-confirmation schemes that rely on knowing which validator will propose a specific block in advance, enabling fast and reliable soft finality assurances.
⚡ Deterministic proposer lookahead is a powerful feature for advanced DeFi applications that need certainty about block confirmations.
On the UX front, EIP-7951 adds a secp256r1 precompile, providing native Ethereum support for P-256 signatures. This curve is used by Apple’s Secure Enclave, Android Keystore, Fast Identity Online 2 (FIDO2), and WebAuthn passkeys. Wallets can leverage device-level biometrics and passkeys instead of seed phrases, bringing layer 1 closer to mainstream fintech login processes.
For developers, EIP-7939 introduces the count leading zeros opcode, which counts leading zeros in a 256-bit word, making bit-level math, big integer arithmetic, and certain zero-knowledge proof circuits more cost-effective and straightforward to implement.
Finally, EIP-7642 extends Ethereum’s history expiry work, allowing clients to discard more pre-Merge and older data while indicating the ranges they serve. This can save hundreds of gigabytes per node and significantly accelerate sync times for new validators.
📌 History expiry is akin to archiving old records, reducing the burden on the system without losing essential information.
Impact on L2s, Validators, and ETH Holders
The benefits of Fusaka for layer-2 ecosystems are clear: PeerDAS and BPO forks work together to lower data costs and increase availability.
Analysts predict that Fusaka, combined with the first BPO fork, could reduce L2 data fees by 40%-60% over time, especially for high-throughput applications like DeFi, gaming, and social platforms. Cheaper blobs create more room for innovation and potentially spark renewed competition among rollups based on price and user experience.
📊 The potential reduction in L2 data fees could unlock new possibilities for decentralized applications and drive greater user adoption.
For node operators and validators, Fusaka brings both advantages and challenges. Sampling and history expiry reduce the amount of data nodes need to download and store, simplifying the process for new nodes to sync to the latest block.
However, as BPO forks increase blob counts, validators and infrastructure providers with sufficient resources will need to handle more upload bandwidth. This could potentially shift the network toward larger operators, emphasizing the importance of careful client implementations and guidance. The Ethereum Foundation is actively working to maintain a decentralized base of validators.
Institutions and staking providers generally view Fusaka as a strategic enabler rather than just a speed boost. More predictable data throughput, safer gas and block size limits, and streamlined history management simplify the planning and execution of large-scale validator operations.
🤔 How will the changes in network bandwidth requirements affect smaller, independent validators? It’s a key question to watch as Fusaka rolls out.
For ETH holders, the impact is direct. Ethereum’s base layer is being optimized as a high-capacity settlement and data engine for L2s, with minimum fees and blob pricing adjusted to encourage more activity on Ethereum. This can influence fee markets and validator rewards, depending on demand.
There are trade-offs, however. The complexity of the protocol increases, and a stronger focus on monetization could face criticism if everyday users do not experience clear improvements in cost and user experience.
Looking Ahead: Glamsterdam and the Path to 100,000 TPS
The next scheduled upgrade, Glamsterdam, is expected in 2026 and already has two primary features in development: enshrined proposer builder separation (ePBS) and block-level access lists (BALs).
- ePBS aims to strengthen the maximal extractable value (MEV) supply chain by separating block building and proposing at the protocol level, rather than relying solely on external relays.
- BALs target more efficient execution and improved state access, including future increases in blob capacity.
PeerDAS and BPO forks advance the Surge, while history expiry extensions and peer-to-peer (P2P) tweaks support the Verge and Purge objectives. User experience upgrades like proposer lookahead and P-256 support make pre-confirmations and passkey wallets more viable at scale.
✅ ePBS and BALs represent critical steps toward optimizing Ethereum’s performance and security in the long term.
If Ethereum maintains this pace of development, Fusaka will be remembered not just as a singular event but as a turning point. It represents the moment when the roadmap evolved into a cohesive and value-driven scaling strategy, aiming to support a 100,000 TPS modular architecture without sacrificing the decentralization that underpins the network’s value.
Frequently Asked Questions About the Ethereum Fusaka Upgrade
What is PeerDAS, and how does it improve Ethereum’s scalability?
PeerDAS (Peer Data Availability Sampling) is a key component of the Fusaka upgrade. It improves scalability by allowing validators to verify rollup data without downloading the entire dataset. It splits data into smaller cells, using sampling and erasure coding to ensure data availability and reduce bandwidth and storage requirements for nodes.
What are Blob-Only Parameter (BPO) forks, and why are they important?
BPO forks are small, targeted hard forks that allow for adjustments to blob-related parameters, such as target size, maximum size, and base fee adjustment factor. They are important because they enable more frequent and smaller adjustments to blob capacity, allowing Ethereum to respond more dynamically to the demands of layer-2 solutions.
How does the Fusaka upgrade benefit ETH holders?
Fusaka benefits ETH holders by tuning Ethereum’s base layer to better support layer-2 solutions, with adjustments to minimum fees and blob pricing designed to encourage more activity on Ethereum. This increased activity will influence fee markets and potentially boost validator rewards and increase the value of holding ETH.
When is the Ethereum Fusaka upgrade expected to be activated?
The Ethereum Fusaka upgrade is scheduled for activation on December 3, 2025. This activation will occur at a specific slot number on the mainnet.
What are the key components of the Ethereum roadmap that Fusaka aligns with?
Fusaka aligns with multiple components of Vitalik Buterin’s Ethereum roadmap, specifically the Surge (scaling through rollups and data availability), the Verge (lighter clients), and the Purge (reducing historical data overhead). It advances all three goals simultaneously, making it a significant milestone in Ethereum’s development.
Final Thoughts on the Fusaka Upgrade
The Fusaka upgrade is an ambitious step forward for the Ethereum network, addressing pressing scalability issues while also enhancing user experience, security, and developer tools. By improving data availability for rollups through PeerDAS and other optimizations, Fusaka paves the way for a more efficient and robust Ethereum ecosystem.
While challenges and trade-offs remain, Fusaka represents a significant milestone in Ethereum’s journey toward becoming a high-throughput, modular blockchain platform capable of supporting a wide range of decentralized applications and use cases. It sets the stage for future upgrades like Glamsterdam and reinforces Ethereum’s commitment to innovation and long-term sustainability.
