Ethereum's Fusaka upgrade will activate on Dec. 3, 2025, at 21:49:11 UTC (epoch 411,392, slot 13,164,544), unleashing a comprehensive package of improvements aimed at scaling, security, and usability. Following the Dencun upgrade, Fusaka marks another critical milestone on Ethereum's roadmap, with a core focus on optimizing L2 data flow and sharpening gas controls.
PeerDAS: A Data Availability Sampling Revolution
The headline feature of Fusaka is PeerDAS, a data availability sampling system. Previously, every full node had to download all blob data to ensure availability—an increasingly unrealistic burden as rollups expand. Under PeerDAS, each node stores just one-eighth of total blob data, reducing disk usage by roughly 80% and cutting download bandwidth significantly. According to Ethereum's roadmap, this shift enables theoretical scaling up to 8x for rollup throughput without crushing node hardware. For L2 users, this translates to lower posting costs and smoother transactions.
Blob-Parameter-Only Forks and Gas Controls
Fusaka introduces Blob-parameter-only (BPO) forks for the first time, allowing blob limit adjustments without waiting for a full network hard fork. Clients can coordinate smaller, blob-focused increments between major releases, offering faster and safer responses to rollup demand. Additionally, a new 16.7 million gas cap per transaction prevents oversized transactions from dominating block space or becoming DoS vectors. The MODEXP precompile also gets updated pricing to prevent underpriced cryptographic operations from bogging down validation. These guardrails make future gas-limit increases less risky.
User Experience and Security Enhancements
On the UX side, Ethereum gains deterministic proposer lookahead, giving clients visibility into upcoming block proposers and enabling preconfirmation flows. Developers get a new EVM opcode—CLZ (count leading zeros)—which simplifies arithmetic and trims gas usage across complex smart-contract logic. Most notably, native support for secp256r1 (P-256) signatures enables passkey-style authentication, allowing wallets to leverage hardware-backed signing features like Apple's Secure Enclave or Android's Keystore, moving beyond traditional seed phrases.
Network and Meta-Layer Improvements
Fusaka tightens network behavior with a 10 MiB RLP block-size ceiling to ensure smooth block propagation, aligns execution and consensus limits, and adds the eth_config RPC method so nodes can cleanly verify upcoming fork settings. These meta-layer updates lay the foundation for future upgrades.
Real Impact for L2 Users
While Fusaka will not meaningfully lower Ethereum L1 gas fees, it significantly expands scaling headroom for rollups—the primary driver of ecosystem throughput. For users on L2s, the upgrade should gradually translate to smoother fees, more resilient infrastructure, and a cleaner path to sustained global growth. Joseph Chalom, CEO of Sharplink, commented on X: “Fusaka is a huge milestone for Ethereum and its path to institutional adoption… It supports the next wave of tokenized assets, institutional settlement, and real financial infrastructure.”
FAQ
- What does Fusaka do? It introduces PeerDAS, new gas rules, better UX features, and expanded scaling support for rollups.
- Will it lower Ethereum gas fees? No meaningful change to L1 fees, but it improves L2 efficiency, potentially easing costs for rollup users.
- Do users need to take action? No steps required; wallets and ETH balances remain fully compatible.
- Why is PeerDAS important? It cuts node data burdens and enables Ethereum rollups to scale up to eight times more efficiently.