Ethereum Fusaka Upgrade

Key Points
The Ethereum Fusaka upgrade is scheduled to launch on the mainnet on December 3, 2025.
Fusaka will raise the block gas limit from 45 million units to 150 million units and introduce new data management technologies such as PeerDAS and Verkle trees.
This upgrade aims to expand Ethereum’s capacity while maintaining decentralization and security.
Multiple testnet phases (Holesky, Sepolia, Hoodi) will be launched before the mainnet rollout.
A four-week bug bounty program with rewards up to $2 million will be held prior to launch.

Introduction
Ethereum has been continuously optimizing and improving to provide a more efficient and user-friendly network experience. The Fusaka upgrade is one of the upcoming major updates, designed to enhance the network’s transaction throughput and overall efficiency.
Expected to be implemented by the end of 2025, Fusaka will not only increase the gas limit but also introduce smarter data processing methods. Below, we outline the content, significance, and future impact of the Ethereum Fusaka upgrade.

What is the Ethereum Fusaka Upgrade?
The Fusaka upgrade is a major network update that expands Ethereum’s transaction processing capacity by raising the block gas limit from 45 million units to 150 million units. This means that with every new block added, the network can accommodate more transactions, smart contracts, and other operations.
But the Fusaka upgrade goes beyond just increasing numbers; it also introduces two key technical improvements:
Peer Data Availability Sampling (PeerDAS): Validators no longer need to download the entire data blob. Instead, they can sample and check small segments from different sources, changing the way data availability and validity are verified.
Verkle Trees: A special blockchain data structure that compresses data proofs into much smaller chunks, allowing for faster verification.
These improvements together enhance Ethereum’s scalability while avoiding excessive burdens on node operators who maintain the network.

Why is the Fusaka Upgrade Critical?
Ethereum has developed rapidly in recent years, with millions of users interacting with DeFi protocols, NFTs, dApps, and Layer 2 solutions. However, during peak periods, the network can become congested, leading to slower transaction confirmations and higher fees.
Fusaka aims to alleviate these issues by:
Allowing each block to accommodate more transactions and more complex operations (increasing block size);
Optimizing the way data is shared and verified, which is especially important for Layer 2 platforms relying on blobs (the data format for publishing transaction information);
Continuing to uphold the network’s decentralization and security to ensure an open and fair experience for all users.
That said, increasing the block size also means that nodes need to process more data, which might be more challenging for some node operators. The PeerDAS and Verkle tree solutions are specifically designed to ease this burden.

Roadmap and Launch Timeline
Fusaka will be implemented in stages, starting with testnet launches and then rolling out to the mainnet:
Holesky Testnet: Planned launch on October 1, 2025
Sepolia Testnet: Planned launch on October 14, 2025
Hoodi Testnet: Planned launch on October 28, 2025
Mainnet launch target date: December 3, 2025 (subject to adjustment based on testnet progress)
Each testnet will help developers validate performance and stability, and fix potential issues before the final mainnet release. Precise dates may be adjusted based on testing outcomes.

What Are the Main Changes?
Peer Data Availability Sampling (PeerDAS)
Traditionally, validators had to download and store large amounts of blob data to validate transactions and maintain blockchain security.
PeerDAS changes this model by allowing validators to randomly sample a small portion of these blobs from different peer nodes. Think of it as reading only some pages of a book rather than reading the entire book cover to cover each time. This lets validators quickly confirm whether the data exists and is correct without downloading everything.
Verkle Trees
Verkle trees replace the current data storage method with a more compact and efficient structure for proving parts of the blockchain state. This improves verification speed, reduces storage requirements, and helps maintain Ethereum’s scalability as the blockchain continues to grow.
Increasing the Gas Limit
A higher gas limit means each Ethereum block can handle more transactions and more complex operations. This is especially important as the network grows and more users want to interact with DeFi, NFTs, and smart contracts.
However, larger blocks also mean nodes require more storage and bandwidth. While Verkle trees and PeerDAS introduced in Fusaka can effectively mitigate the added burden, node operators still need to closely monitor related changes and update their setups as needed.

What Does Fusaka Mean for Users, Developers, and Validators?
Users: As network capacity improves, transaction confirmation times during peak periods may become faster. Gas fees may become more predictable but will still fluctuate based on network demand.
Developers: Larger blob capacity and PeerDAS will improve how rollups (Layer 2 scaling solutions) submit data to Ethereum, making the process more reliable and efficient.
Validators and Node Operators: With data sampling, validators don’t need to download all blob data, reducing bandwidth usage. Note that necessary network configuration and updates will be required to support these changes.

Security and Bug Bounty
Given the critical importance of security for Ethereum upgrades, the Ethereum Foundation will run a four-week bug bounty program before Fusaka goes live. With rewards up to $2 million for discovering critical vulnerabilities, the program aims to encourage thorough community review and strengthen code security.

Conclusion
The Fusaka upgrade is a key step forward for Ethereum in increasing transaction throughput and overall efficiency. By raising the gas limit and introducing smarter data validation technologies such as PeerDAS and Verkle trees, this upgrade supports future scalability while upholding Ethereum’s commitment to decentralization and security. () ‌