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Scalability at the center: with Fusaka, Ethereum aims to increase throughput by raising the block gas limit from 30 million to 150 million and adopting techniques that lighten the data verification load. The goal remains clear: to expand capacity without affecting decentralization and security.
The activation on the mainnet is provisionally set for December 3, 2025, as indicated in the recent All Core Developers Consensus (ACDC) Call #165.
According to data collected from preliminary testnet telemetry and official communications, the increase in gas per block corresponds to a theoretical throughput increase of +400% compared to the previous value (from 30M to 150M). The Ethereum Foundation and protocol reports also indicate that the changes in blob management — including PeerDAS techniques — aim to scale blob capacity significantly, moving from current parameters to targets that can lead up to 48 blobs per block (x8 compared to 6 blobs), with direct impacts on rollup and L2.
Summary
Key Numbers
- Gas limit per block: from 30,000,000 to 150,000,000 (400% increase)
- Testnet: Holesky (October 2, 2025), Sepolia (October 16, 2025), Hoodi (October 30, 2025)
- Mainnet: target on December 3, 2025
- Blob capacity: estimate of a doubling within two weeks of activation; project goals indicate capacity up to 48 blobs/block (up to 8x compared to 6 blobs)
- Bug bounty: 4-week window, maximum reward 2,000,000 USD
Why it matters: tangible impact
The increase in the gas limit expands the capacity per block. In parallel, new data sampling techniques lighten the load on nodes, impacting traffic distribution. The expected result is a network capable of handling more operations and a more streamlined data pipeline.
The theme of trade-offs remains: larger blocks can lead to additional requirements in terms of storage and bandwidth for the nodes. That said, developers aim to mitigate these impacts with optimizations in data management and verification procedures.
Roadmap and Activations
The rollout sequence involves transitioning from testnets to the mainnet. The scheduled dates may vary based on the results of the tests and post-activation checks.
- Holesky: activation scheduled for October 2, 2025
- Sepolia: activation scheduled for October 16, 2025
- Hoodi: activation scheduled for October 30, 2025
- Mainnet: target on December 3, 2025 (to be confirmed with epoch and times)
After each activation, a telemetry analysis and thorough checks on network performance and stability are scheduled. Only after these steps will the final dates be confirmed.
What changes under the hood
Peer Data Availability Sampling (PeerDAS)
With PeerDAS, validators do not need to download the entire blob: they perform a sampling of small portions from peers, speeding up verification and reducing the required bandwidth. In this context, the approach described in EIP-7594 improves data availability, especially for Layer 2 solutions that use blobs for calldata.
Verkle Trees
The Verkle Trees allow for compressing state proofs, making them more compact and quicker to verify. Along with PeerDAS, this innovation aims to simplify node storage and speed up access to state portions, pushing Ethereum towards greater scalability.
Gas limit at 150M: opportunities and risks
The increase of gas per block to 150M paves the way for higher throughput, essential for complex transactions and intensive on-chain operations. However, the increase in requirements could impact costs and node management; efforts are being made to balance this effect with the introduction of systems like PeerDAS.
These mechanisms aim to reduce latency and verification overhead, thereby containing the potential indirect costs associated with increased capacity.
What changes for…
- Users/DeFi: potential improvements in congestion and confirmation times during activity peaks. Fees will still depend on demand, without a guaranteed structural decrease.
- L2 Developers: more efficient blob publishing and greater reliability in data availability, crucial aspects for high-throughput rollups.
- Validators/operators: reduced need to fully download blobs thanks to sampling, with possible updates related to bandwidth and network configurations.
Security: auditing and bug bounty
The Ethereum Foundation has launched a auditing contest lasting four weeks to subject Fusaka to rigorous tests before the fork. The initiative, which offers rewards up to 2,000,000 USD for the discovery of critical vulnerabilities, aims to strengthen the robustness of the code with the contribution of the security researchers community.
Estimates on blob and performance
According to technical discussions and protocol notes, the blob capacity could double in the two weeks following activation in conservative scenarios; however, project goals indicate wider margins (up to 48 blobs/block) depending on adoption and telemetry collected on testnets. These are preliminary estimates, based on expected traffic models and telemetry, and are pending further confirmation on testnet.
Quick Glossary
- Gas limit: maximum amount of work that a block can contain, with direct impacts on capacity and costs.
- Blob: economically published data packets, primarily used by rollups.
- Epoch: time interval used to coordinate network activations and purposes.
- PeerDAS: technique for verifying data availability by sampling portions from multiple peers.
- Verkle Trees: data structure that allows for more compact state proofs.
Quick FAQ
What is the next version after Fusaka?
A release named Glamsterdam is scheduled for 2026, focusing on further scalability optimizations, including the full implementation of the EOF (EVM Object Format) and possible improvements in block times. The details are currently under discussion.
In summary
Fusaka combines an increased gas limit with innovations in data management and cryptographic proofs. The integration of PeerDAS and Verkle Trees aims to balance capacity and decentralization, with a roadmap starting from testnets to reach the mainnet on December 3, 2025. The dates, although provisional (updated as of 09/19/2025), will be confirmed after thorough testing on Holesky, Sepolia, and Hoodi.