The Ethereum roadmap continues to unfold with the Fusaka upgrade, set to follow the Pectra hard fork. Planned for the fourth quarter of 2025, Fusaka is an important step forward, designed to improve the experience for both Ethereum users and developers. It's an infrastructure-focused update, introducing new features aimed at enhancing scalability and network efficiency.
This post breaks down the key components of the Fusaka upgrade. You will learn about the major changes, including Peer Data Availability Sampling (PeerDAS), new safety limits, and tools for developers. By the end, you'll have a clear understanding of what Fusaka is, how it works, and why it matters for the future of Ethereum and its Layer-2 ecosystem.
Key Features and Enhancements
Fusaka is a collection of about a dozen Ethereum Improvement Proposals (EIPs) that make the protocol faster, leaner, and cheaper to use. These changes primarily benefit Layer-2 networks like Arbitrum, Optimism, and Base, which now handle most of Ethereum's activity.
Peer Data Availability Sampling (PeerDAS)
PeerDAS is the headline feature of the Fusaka upgrade. Currently, Layer-2s post their transaction data to Ethereum in packages called "blobs." Every full node must download all of this data to verify it. As L2s grow, this creates a data bottleneck.
PeerDAS changes this by allowing nodes to check small, random samples of the data instead of downloading everything. This approach dramatically reduces the data that nodes need to check, which could enable up to an eight-fold increase in data space over time. More data space leads to lower competition, which in turn reduces transaction fees on Layer-2s.
Blob-Parameter-Only (BPO) Forks
As Layer-2 networks expand, they require more data space on Ethereum. To meet this demand without waiting for major hard forks, Fusaka introduces Blob-Parameter-Only (BPO) forks. These are small, focused updates that allow the network to incrementally raise blob targets between larger upgrades. This flexibility helps Ethereum adapt more quickly to the growing needs of L2s.
Safety and Performance Hardening
To handle increased activity safely, Fusaka adds several new network regulators:
Caps on per-transaction gas to prevent a single transaction from consuming an entire block.
Tighter MODEXP limits and revised pricing for certain heavy computational operations to prevent abuse.
A 10 MiB RLP block size cap to prevent spam and keep nodes running smoothly.
History expiry support to help nodes stay lean by allowing them to ignore very old historical data. Execution clients began supporting partial history expiry in July 2025.
New Developer Features
Fusaka also brings powerful new tools for developers:
Secp256r1 precompile enables wallets to use your phone's built-in security features, like Face ID or fingerprint sensors (passkeys), to approve transactions.
The CLZ opcode adds an instruction for counting leading zeros, making complex on-chain math cheaper and more efficient for advanced applications.
Key EIPs in the Fusaka Upgrade
The Fusaka upgrade is composed of several key EIPs that deliver these improvements. Here are some of the most important ones included in the fork:
EIP-7594 (PeerDAS): Enables nodes to verify L2 data by sampling instead of downloading everything.
EIP-7892 (Blob Parameter Only Hardforks): Creates a mechanism to increase L2 data space between major upgrades.
EIP-7951 (Precompile for secp256r1 Curve Support): Allows wallets to use device-native security like Face ID.
EIP-7939 (Count Leading Zeros Opcode): Adds a tool for more efficient on-chain math.
EIP-7825 (Transaction Gas Limit Cap): Prevents any single transaction from monopolizing a block.
EIP-7934 (RLP Execution Block Size Limit): Sets a hard limit on the physical size of a block to prevent spam.
EIP-7823 & EIP-7883 (MODEXP Bounds and Gas Cost Increase): Adjusts the cost of a specific function to reflect its computational weight and prevent abuse.
EIP-7917 (Deterministic Proposer Lookahead): Makes the network more predictable, enabling near-instant L2 confirmations.
EIP-7918 (Blob Base Fee Bounded by Execution Cost): Adjusts the blob fee market to maintain price stability during high L1 congestion.
EIP-7642 (History Expiry and Simpler Receipts): Allows nodes to prune very old history, simplifying the sync process.
EIP-7935 (Set Default Gas Limit to 60M): Increases the computational capacity of each block on the main network.
EIP-7910 (eth_config RPC Method): Adds a tool for node operators to verify their upgrade configuration.
Fusaka Upgrade Timeline
Fusaka will be deployed in phases, beginning with testnet activations before the mainnet launch:
Holesky testnet: Activation planned for October 1, 2025
Sepolia testnet: Activation planned for October 14, 2025
Hoodi testnet: Activation planned for October 28, 2025
Mainnet target date: December 3, 2025 (dates subject to change based on testnet results)
How Fusaka Impacts You
The Fusaka upgrade is a technical hard fork focused on improving Ethereum's core infrastructure. Here’s what it means for different groups in the ecosystem:
For Users: You don't need to take any action. You will experience the benefits indirectly through faster and cheaper transactions on Layer-2 networks. New apps will also be able to use your phone's biometrics for a simpler and safer user experience.
For Developers & L2 Teams: Fusaka offers cheaper data and new tools, like passkey support and the CLZ opcode. These changes reduce gas costs and simplify development for applications using advanced logic.
For Node Operators: The only action required is to update your client software to a Fusaka-compatible version before the mainnet activation date of December 3, 2025.
The Fusaka upgrade helps Ethereum handle more transactions and operate more efficiently. It increases the gas limit and adds smart data verification with PeerDAS and Verkle Trees. This change supports future growth while keeping Ethereum secure.
As with any upgrade, be aware of scams. No one will ever ask you to "upgrade" your ETH. Your assets are safe, and no action is needed on your part to protect them.
What’s Next for Ethereum
Following Fusaka, the Ethereum roadmap continues with the "Glamsterdam" upgrade, planned for 2026. This next upgrade will further Ethereum's scalability, security, and sustainability. Specific EIPs and technical details have not yet been announced.
Frequently Asked Questions (FAQs)
What is Fusaka, and why is it important?
Fusaka is a major upgrade in the Ethereum roadmap designed to enhance security, scalability, and overall network efficiency. It represents a critical step toward ensuring Ethereum remains a leader in decentralized technology while preparing for future innovations.
Do I need to take any actions to prepare for the Fusaka upgrade?
No action is required on your part. Your ETH and other assets remain safe throughout the process. Be cautious of scams. No one will ask you to upgrade your ETH or move it elsewhere for the upgrade.
How does Fusaka improve Ethereum’s scalability?
Fusaka introduces optimizations that reduce network congestion and improve transaction speeds. This enables Ethereum to handle more transactions per second, setting the foundation for a more scalable ecosystem.
What comes after Fusaka?
The next planned upgrade is Glamsterdam, scheduled for 2026. While specific details of Glamsterdam are still under discussion, it aims to further improve Ethereum's scalability, security, and environmental sustainability.
Will my existing Ethereum applications or smart contracts be affected by Fusaka?
No, your existing Ethereum applications or smart contracts will continue to operate as usual. The upgrade ensures backward compatibility while offering enhanced functionality and performance benefits for developers and users alike.
