Written by: Tanay Ved, Coin Metrics
**Translated by: **GaryMa Wu Says Blockchain
Key Takeaways
Fusaka expands Ethereum's scalability by increasing blob capacity and implementing a more efficient data availability system (PeerDAS).
A higher gas limit of 60 million and optimizations in the execution layer significantly enhance L1 throughput.
Improved fee mechanisms and UX upgrades lay the foundation for a more unified and cost-effective L1–L2 ecosystem.
Overview of Fusaka
Ethereum will experience the "Fusaka" hard fork on December 3, 2025, at 21:49 UTC (slot 13,164,544). Fusaka merges the execution layer upgrade Osaka with the consensus layer upgrade Fulu, continuing the naming convention of past forks.
Following May's Pectra, Fusaka is a significant step in Ethereum's scalability roadmap: enhancing L1 performance, expanding blob capacity, improving rollup cost efficiency, and bringing UX improvements. It also introduces the Blob Parameter Only (BPO) fork mechanism to safely increase blob capacity as rollup demand grows. Earlier this year, the Ethereum Foundation announced the "Protocol" strategy, focusing on three long-term goals: scaling L1, expanding blobs, and enhancing user experience. Fusaka is the first upgrade fully aligned with this unified vision, marking a turning point for Ethereum's future scalability and accessibility improvements.
This article will outline the key changes in Fusaka and analyze its impact on the Ethereum mainnet, Layer-2 rollups, transaction costs, and user experience.
Expanding Blobs
Last year's Dencun upgrade introduced "blobs," allowing rollups to store transaction data on the Ethereum mainnet at a lower cost. Since its launch, blobs have seen significant adoption thanks to rollups like Base, Arbitrum, and Lighter. This has led to blob usage often nearing saturation (currently close to the target of 6 blobs per block), potentially triggering exponential increases in rollup fees. As the demand for data availability continues to grow, blob space has become a critical bottleneck in Ethereum's scalability path, which Fusaka directly addresses.
PeerDAS: Peer Data Availability Sampling
PeerDAS (EIP-7594), or Peer Data Availability Sampling, is arguably one of the most important upgrades in Fusaka, directly corresponding to the core goals of scaling L1 and expanding blobs. PeerDAS introduces a more efficient method for Ethereum nodes to verify the availability of blob data. Nodes do not need to download the entire blob content but can check availability by sampling data fragments, maintaining the same level of security without increasing the burden on L1 consensus nodes.
Expected Impact:
Nodes only need to store about 1/8 of each blob, significantly increasing blob throughput without raising hardware requirements.
Enables Ethereum to safely increase blob throughput, which is a core driver of rollup capacity.
Lower data availability costs lead to cheaper L2 transactions and more reliable batch submissions.
Lays the groundwork for complete danksharding, enhancing the overall ecosystem's transaction throughput. For example, Base mentioned in a blog that improvements in L2 scalability after Fusaka will allow it to "double the chain's throughput within 2 months."
Blob Parameter Only (BPO) Fork
With PeerDAS reducing the bandwidth and storage burden for nodes verifying blob data, Ethereum can now safely increase blob capacity. Fusaka introduces the Blob Parameter Only (BPO) fork mechanism to gradually raise the blob limit per block over time. This mechanism allows Ethereum to adjust blob parameters without a complete hard fork, providing a more flexible and responsive means of scaling the protocol.
Upcoming BPO Fork
Expected Impact:
Higher DA Bandwidth: Increases rollup capacity from 6 blobs to 128 blobs per block, significantly reducing L2 transaction fees.
Flexible Scaling: Blob parameters can be dynamically adjusted as demand grows.
Incremental Scaling Path: Aligns with Ethereum's roadmap for cheaper rollup execution and scalable data availability.
Blob Base Fee Adjustment
As blob capacity expands, Ethereum's blob fee market will play a more significant role in coordinating rollup demand. Currently, rollups pay almost no cost for blobs. Due to demand being price insensitive, blob fees typically remain at the minimum of 1 wei, and prices do not always adjust smoothly with usage changes. This has led to a "price inelastic" state in the fee mechanism, limiting its responsiveness to usage changes.
Fusaka avoids blob prices dropping to zero by linking the lower limit of the blob base fee to a fixed ratio of the L1 base fee, ensuring that the fee adjustment mechanism continues to operate effectively as blob space expands.
Key Impacts:
More Stable Blob Pricing: Prevents the fee market from getting stuck at the lowest price.
More Predictable Rollup Economics: Ensures rollups pay a reasonable baseline for data availability without sudden or unstable fee fluctuations.
Minimal Impact on User Costs: Even with a lower limit, L2 data costs remain just a fraction of a few cents, having almost no effect on UX.
Long-term Economic Sustainability: Compensates nodes for handling higher blob throughput costs; currently, blob fees contribute little to ETH burning, but as capacity expands, they may contribute more.
Scaling L1
Fusaka also places significant emphasis on L1 scaling. Through EIP-7935, it raises Ethereum's default gas limit to 60 million, enhancing Layer-1 execution capacity. This directly increases the number of transactions that can fit in each block, achieving higher throughput, less congestion, and lower gas fees.
Expected Impact:
Higher Throughput: More computations can be performed per block, increasing overall L1 capacity.
Supports More Complex Applications: A larger gas limit allows complex contracts to execute smoothly.
Less Congestion Under High Load: Additional space reduces congestion during demand spikes.
Maintains Low Fees: Extra capacity supports the current low fee environment (0.4 gwei).
In addition to raising the gas limit, Fusaka introduces a series of optimizations to make L1 execution more efficient and prepare for future scaling.
New Single Transaction Gas Usage Limit: Prevents a single transaction from occupying the entire block space and lays the groundwork for future parallel execution.
ModExp Precompile Optimization: Recalibrates gas costs and sets clearer boundaries for related operations, ensuring resource usage remains predictable as throughput grows.
Network Layer Streamlining: Removes deprecated pre-merge fields, allowing Ethereum nodes to sync faster and lighter.
Enhancing User Experience (UX)
Fusaka introduces a series of updates to improve the experience for users and developers. Among them, EIP-7951 adds native support for the secp256r1 elliptic curve, a signature standard widely used by Apple Secure Enclave, Android Keystore, and most consumer-grade hardware.
This means wallets and applications can directly integrate familiar authentication processes on Ethereum, such as Face ID, Touch ID, and WebAuthn.
This reduces user onboarding friction and provides stronger security for retail and institutional users.
These upgrades further modernize Ethereum's developer experience and user interface, making it easier to build secure, mainstream applications.
Conclusion
With the activation of Fusaka, the most immediate impacts will be: lower rollup costs; higher blob throughput; and significantly enhanced L1 execution capacity.
Over time, greater blob space, lower costs, and steady improvements in L1 performance will reshape L2 settlement economics, influence ETH burning dynamics, and create a more unified and coordinated Ethereum ecosystem.
While the long-term value impact still depends on demand and adoption speed, Fusaka lays a clearer and more scalable foundation for the next phase of Ethereum's growth: an ecosystem where L1 and L2 work more efficiently together, capable of supporting more users, assets, and on-chain activities.
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