Ethereum developers reached a big milestone this week. They launched the Fusaka upgrade on the Sepolia testnet, the second major test after the successful run on Holesky. Next comes the final test on Hoodi, which will pave the way for the main network launch. If you are wondering what is changing and why it matters, here is the full story.

What Is the Fusaka Upgrade?

Fusaka is a major Ethereum network upgrade that increases the block gas limit from 45 million to 150 million, enabling the network to process significantly more transactions and smart contracts per block. At its core, the upgrade introduces two game-changing technologies: PeerDAS and Verkle Trees.

PeerDAS (Peer Data Availability Sampling)

PeerDAS (Peer Data Availability Sampling) is a new data verification method that allows validators to verify only small portions of data instead of downloading entire data blobs. This seemingly small change has massive implications.

Verkle Trees

Verkle Trees compress data proofs into smaller, faster-to-check pieces, making the whole system more efficient.

What are the Core Benefits of the Fusaka Upgrade?

1. Efficiency and Cost Reduction

Streamlined Validator Workload:
Fusaka reduces the amount of data validators need to process and verify, making block validation more lightweight.

Lower Operational Costs:
This optimization directly reduces hardware and bandwidth costs for validators and Layer-2 operators.

2. Institutional Appeal

Scalable Infrastructure Advantage:
By lowering the cost and complexity of running validator infrastructure, Ethereum becomes more appealing to institutional users managing nodes or staking operations at scale.

Operational Flexibility:
Enterprises can maintain or expand participation in the network without heavy infrastructure upgrades.

3. Technical Improvements

12 Major Code Updates:
Fusaka introduces a dozen significant code-level changes aimed at improving scalability and network performance.

Layer-2 Optimization:
Transaction costs on Layer-2 rollups are reduced, promoting faster and cheaper scaling solutions.

4. Security and Stability

No Compromise on Security:
Despite cutting infrastructure demands, the upgrade maintains Ethereum’s strong security guarantees.

Balanced Ecosystem Growth:
The combination of efficiency and safety makes Fusaka a win-win for both individual validators and the broader Ethereum ecosystem.

Why Did They Test It on Sepolia First?

Here’s how Ethereum actually works—they don’t just roll out upgrades and hope for the best. They test everything on multiple testnets before touching mainnet where real money lives. That’s where Sepolia testnet comes in.

The Sepolia launch has given developers another chance to see how Fusaka performs. Coming just two weeks after Holesky’s successful test, Sepolia reinforced confidence that the upgrade is stable.

Developers got to watch how the system behaves, spot any issues, and make sure everything works as planned before it ever touches the main blockchain.

What Makes Hoodi Different from Previous Testnets?

Hoodi stands out from earlier testnets because it was built to closely mirror the real Ethereum main network.

Unlike older testnets like Holesky, Hoodi’s setup and parameters match mainnet conditions much more accurately. This means any testing done on Hoodi gives developers a realistic picture of how the upgrade will perform once it’s live for everyone.

Ethereum’s upgrade process is always intentional~ start with smaller testnets, then move to ones that feel more like the real thing. Hoodi is that final stage, the last checkpoint before the Fusaka upgrade officially launches on mainnet.

When Will Fusaka Actually Go Live?

The Hoodi testnet was successfully activated on October 28, 2025, marking the final step before Ethereum’s next big upgrade goes live on the main network.

After the smooth trial, Ethereum’s core developers confirmed during the All Core Devs call on October 30 that the Fusaka upgrade will officially launch on December 3, 2025.

This fast-paced testing process moving from devnet to Holesky, Sepolia, and finally Hoodi shows how efficiently Ethereum’s team works while maintaining high technical standards.

Fusaka continues Ethereum’s commitment to steady improvement.

The upgrade includes 12 major improvements aimed at making Layer 2 networks faster and cheaper, doubling blob capacity, and enabling near-zero-cost transactions. With Hoodi completed and no major issues reported, the network is now ready for its mainnet debut.

The Bottom Line

In short, Hoodi is the final and most accurate testnet before the Fusaka upgrade officially launches on Ethereum’s main network. It gives developers a true picture of how the upgrade will perform once live.

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Frequently Asked Questions

What is Fusaka Ethereum upgrade?

Fusaka is a major Ethereum upgrade that increases the block gas limit from 45 million to 150 million. It introduces PeerDAS and Verkle Trees technologies that allow validators to verify data more efficiently, reducing costs and making the network faster and cheaper to operate.

When does Fusaka go live on mainnet?

Fusaka is officially scheduled for mainnet activation on December 3, 2025, after successfully completing testing on Sepolia and Hoodi testnets.

How will Fusaka reduce transaction fees?

Fusaka increases Ethereum’s block capacity to 150 million gas, allowing more transactions to fit into each block. This reduces competition in the fee market and lowers transaction costs, especially during network congestion. Layer 2 networks also benefit from cheaper data posting costs.

What is PeerDAS in Fusaka?

PeerDAS (Peer Data Availability Sampling) is a technology in Fusaka that allows validators to verify only small portions of data instead of downloading and verifying entire data blocks. This significantly reduces bandwidth demands and validator costs.

Why did Ethereum test Fusaka on Sepolia testnet?

Sepolia is a reliable testnet environment where developers can validate Fusaka’s performance under real-world conditions before deployment on mainnet. Testing on testnets catches issues early and ensures the upgrade is stable before it affects real users and money.

What is Hoodi testnet and why is it important?

Hoodi is Ethereum’s newest testnet built to closely mirror mainnet conditions. It was the final testing ground for Fusaka because its environment and parameters align with the main network, making stress tests far more representative of real-world performance after mainnet activation.