Fusaka Ethereum upgrade explained: PeerDAS and cheaper L2s

Fusaka combines Ethereum’s execution layer upgrade, Osaka, and the consensus layer version Fulu. Following Ethereum’s post-2021 naming pattern, the upgrade is named after a Devcon city and a celestial star, signaling changes in both the execution and consensus layers.

Ethereum’s previous upgrade, Pectra, launched in May 2025, adding better wallet features and more flexible staking. Fusaka is now in development, with mainnet activation expected around December 2025, once testnets are successfully completed.

Inside the Ethereum Fusaka Upgrade

The Fusaka Ethereum upgrade builds on the momentum of previous upgrades like Dencun and Pectra, focusing on scalability, node health, and infrastructure resilience. It’s part of Ethereum’s post-Merge roadmap and follows the network’s switch from Proof-of-Work to Proof-of-Stake in September 2022. Fusaka arrives about six months after Pectra, further increasing scalability through 12 Ethereum Improvement Proposals (EIPs), mainly focused on Layer 2s – blockchains built on top of Ethereum that make transactions faster and cheaper. 

Fusaka’s key components include:

• PeerDAS (Peer-to-Peer Data Availability Sampling): This is the key feature of the Ethereum Fusaka upgrade, introduced as EIP-7594. Normally, every validator on Ethereum must download and store large chunks of data for each block, which can slow the network. PeerDAS applies data availability sampling (DAS) – a technique that allows Ethereum to handle more data without overloading individual validators. Instead of every validator checking all the data, the work is shared across the network – different computers verify small random pieces. Together, they confirm that all data is available and correct without anyone needing to download everything. This makes Ethereum faster and lighter to operate and could raise transaction speeds to around 200–300 transactions per second, up from roughly 140 today. It also expands the capacity of Layer 2 rollups by giving them more room to store and verify data from the main network.

• Blob capacity growth: In Ethereum, a blob is a chunk of data that Layer 2 networks post to the main network to ensure security and data availability. As Layer 2s grow, they need to post more blobs, which means Ethereum must gradually increase how many blobs it can handle. When blobs were first added in the Dencun upgrade, the target was 3 per block. Pectra increased it to 6, and after Fusaka, blob parameter only (BPO) forks allow the network to continue raising blob limits safely and gradually, keeping up with the growing needs of Layer 2 networks.

• Gas improvements: Gas is what powers every action on Ethereum – from sending tokens to running smart contracts. The higher the gas limit, the more activity the network can process in each block. Fusaka refines how gas works to make transactions smoother and more balanced. EIP-7935 raises the default gas limit, allowing more transactions and complex smart contract activity per block. EIP-7825 caps individual transactions at 30 million gas to prevent network congestion, while EIP-7883 adjusts cryptographic costs to make computation more accurate and efficient.

Before its mainnet deployment, Fusaka is tested on several public testnets, including Holesky, Hoodi, and Sepolia, with a target mainnet activation around late 2025. 

Why Fusaka could be a game-changer 

Fusaka marks an important step for Ethereum, addressing two long-standing challenges – scalability and transaction costs. It focuses on making the network more efficient, especially for Layer 2 rollups, which handle much of Ethereum’s activity and are essential for wider adoption.

Since the Dencun upgrade introduced blobs, their usage has grown rapidly, in some cases reaching the current target of six blobs per block. When this limit is hit, Layer 2 fees rise, and transactions can slow down. Ethereum co-founder Vitalik Buterin noted on X that the Fusaka upgrade could “help fix the blob problem,” allowing Ethereum to scale rollups safely as demand grows. Buterin strongly emphasized a cautious and phased approach to implementing Fusaka, stressing that safety first is of the utmost importance. He wrote: “This is all new technology, and the core devs are wise to be super cautious on testing, even after they have been working on this for years…. This is also why the blob count will increase conservatively at first, and then become more aggressive over time.”

Fusaka’s improvements, particularly PeerDAS and Blob-Parameter-Only forks, enable Ethereum to process more data per block without overloading node operators. This means faster transaction processing, support for more complex smart contracts, and stronger performance across active Layer 2 networks.

For users, these changes translate to lower fees, faster confirmations, and smoother app experiences. With lighter data requirements, mobile wallets and dApps become more responsive, making Ethereum faster and easier to use on everyday devices.

How Fusaka impacts users, builders, and validators

The Fusaka upgrade is set to bring benefits for users, developers, and validators. For everyday users, it makes the network more reliable and smoother to use. Transactions are less likely to fail or get delayed, and higher Layer 2 capacity means apps can handle more activity without slowing down. 

These improvements also open doors for businesses and institutions to adopt Ethereum, as they can trust the network to handle large-scale operations efficiently and securely. Large financial firms, including those managing crypto exchange-traded products (ETPs) and digital asset treasuries (DATs), are already buying and staking ETH to earn rewards. Analysts from VanEck see this as proof that ETH is becoming a valuable long-term asset, not just something that generates fees, making it more attractive for institutional investment funds and ETFs. 

For developers, the Fusaka upgrade Ethereum creates new opportunities but requires careful planning. With larger blob capacity and smoother Layer-2 integration, they can build more advanced decentralized apps (dApps), experiment with complex smart contracts, and scale their applications beyond previous limits. However, developers need to stay updated on changing parameters like gas limits and blob handling to ensure their apps remain efficient and compatible.

Validators benefit from Fusaka as well. Features like PeerDAS and BPO forks make data verification easier and more balanced, reducing their workload while keeping the network secure. This makes running a node more manageable and encourages long-term participation in Ethereum’s Proof-of-Stake system.

Overall, Fusaka strengthens the network’s value for all participants, from everyday users to institutions, by making it more reliable, scalable, and ready for high-volume operations. Looking ahead, the next upgrade, Glamsterdam, aims to further improve network efficiency and scalability.