What Ethereum’s Fusaka Upgrade Changes for zkRollups

Ethereum’s Fusaka upgrade is a rollup-centric change. It does not modify zk proof systems, but instead changes the conditions under which zkRollups operate: how much data they can post to Ethereum, how that data is priced, and how much work the base layer can safely handle.

For anyone using zkRollups, Fusaka is about making L2 blockspace cheaper and more scalable while keeping @Ethereum’s security and decentralization intact.

How zkRollups Actually Use Ethereum

A zkRollup depends on Ethereum for two core things:

• Settlement and verification - posting succinct proofs so Ethereum can check that the rollup’s state transitions are valid.
• Data availability - publishing enough transaction and state data that anyone can reconstruct the rollup’s state if needed.

Since Dencun, that DA step has used special “blob” space attached to blocks. Blobs are cheaper than normal calldata but still counted as a shared resource. For many rollups, blob usage is the dominant cost and the main ceiling on throughput.

Before Fusaka, every full node had to download all blob data. That meant Ethereum had to be conservative about how many blobs per block it allowed and how fast it could increase those limits, because every extra blob directly raised node bandwidth and storage requirements. Even with good compression, the base-layer DA capacity remained the tightest constraint.

PeerDAS: Raising the Data-Availability Ceiling

Fusaka introduces PeerDAS, a data-availability sampling scheme for blobs.

In practice, this means:

• Blob data is erasure-coded and split into many pieces.
• These pieces are distributed across the network instead of being fully stored by every node.
• Each node stores and serves only a small fraction of the encoded data and samples from peers to verify that the full blob is available.

If sampling succeeds, the protocol can treat the blob as available with high confidence. If it fails, the blob is unsafe and will not be accepted.

The important consequence is that total blob throughput can grow much faster than per-node load. Ethereum can raise blob limits over time without forcing everyone to upgrade to data-centre hardware.

For zkRollups, this directly translates into:

• More room to publish batches and state updates.
• A clearer path to higher aggregate L2 throughput, still backed by Ethereum’s DA guarantees.
• Less fear that rollup growth will immediately hit a hard DA wall at L1.

Blob Fees: Cheaper and More Predictable Rollup Costs

The next piece is the blob fee market.

Post-Dencun, blob pricing had some awkward behaviour. Blob fees could sit near zero for long periods even when the execution layer was busy, then jump sharply when demand spiked. That made economic planning tricky and encouraged designs that implicitly assumed “DA is practically free” in the long run.

Fusaka changes this by tying blob fees more tightly to overall network conditions, so they cannot stay unrealistically low while the chain is congested. It pairs that with higher blob capacity from PeerDAS, so extra demand can be met by more supply rather than only by higher prices.

For zkRollups and their users, the effect is:

• Lower average DA cost per unit of data as capacity increases.
• More stable and predictable blob fees, so rollup fees are less prone to weird edge-case behaviour.
• A better environment for high-frequency use cases - payments, trading, gaming, agent traffic - where per-transaction L1 DA cost really matters.

From a user perspective, you mostly see this as L2 transactions trending cheaper and fee spikes becoming less extreme.

More Execution Room for Rollup Infrastructure

zkRollups also depend on Ethereum for on-chain components:

• Bridges and deposit/withdrawal logic.
• Proof verification contracts.
• Cross-rollup messaging hubs and shared sequencers.

Fusaka increases the overall block gas limit, giving more total computation per block, but introduces hard caps on gas per transaction and on encoded block size. This combination gives more space for all the settlement, bridge, and coordination logic rollups need, whilst preventing single oversized transactions or pathological blocks from monopolising resources or breaking block propagation.

The base layer becomes a more capable hub for many rollups to share, without sacrificing the property that a regular machine can still run a validating node.

Proposer Lookahead and UX

Fusaka also improves deterministic visibility into upcoming block proposers.

With clearer proposer lookahead, Rollups and shared sequencers can better plan when they post blobs and settlement transactions. They can also design stronger preconfirmation schemes, where users get early, Ethereum-aligned assurances about inclusion.

For users, the technical details are abstracted away. The tangible outcomes are fewer surprises around delayed inclusion or occasional rollbacks and smoother UX for applications that advertise fast, but still Ethereum-secured, finality on L2.

Why This Is Good for Ethereum and zkRollups

At the network level, Fusaka pushes Ethereum deeper into its rollup-centric roadmap in a controlled way:

• It scales the resource rollups need most - data availability - without centralising nodes.
• It makes the fee market for that resource more rational and more closely linked to real demand.
• It increases total execution capacity while enforcing hard limits that protect safety and decentralisation.
• It provides better coordination hooks for rollups to align UX with Ethereum’s consensus.

For zkRollups specifically, one of the hardest fundamental constraints is relaxed. DA on Ethereum becomes less of a fixed ceiling and more of a scalable resource. The limiting factors shift back toward where they belong: proving performance, aggregation, and product design.

For everyone else - the people just trying to use Ethereum through L2s - the implication is this: zkRollups get more headroom to grow, fees have more room to fall, and Ethereum stays credibly decentralised while it happens.