Ethereum Fusaka Upgrade Set for December 3 Mainnet Launch, Blob Capacity to Double

Ethereum developers confirmed the Fusaka upgrade will activate on mainnet on December 3, 2025, following a systematic testnet rollout beginning on October 1 on ￰0￱ major hard fork will implement around 11-12 Ethereum Improvement Proposals targeting scalability, node efficiency, and data availability improvements without adding new user-facing ￰1￱ to Christine Kim , the upgrade introduces a phased blob capacity expansion through Blob Parameter Only forks occurring two weeks after Fusaka ￰2￱ maintaining current blob limits of 6/9 target/max, the first BPO fork will increase capacity to 10/15 blobs one week later. A second BPO fork will further expand limits to 14/21 blobs, more than doubling total capacity within two ￰3￱ decisions were made on today's Ethereum developer call, ACDC #165.

Developers confirmed the public testnet schedule and BPO hard fork schedule for Fusaka. Let's get into ￰4￱ — Christine ￰5￱ (@christine_dkim) September 18, 2025 Strategic Infrastructure Overhaul Fusaka prioritizes backend protocol improvements over user-facing features, focusing on making Ethereum faster and less ￰6￱ upgrade includes PeerDAS implementation through EIP-7594 , allowing validator nodes to verify data by sampling small pieces rather than downloading entire ￰7￱ reduces bandwidth and storage requirements while enhancing Layer 2 rollup ￰8￱ upgrade builds on recent gas limit increases from 30 million to 45 million gas, with ongoing discussions for further expansion.

EIP-7935 proposes increasing limits to 150 million gas, potentially enabling significantly higher transaction ￰9￱ improvements complement broader scalability efforts, including EIP-9698 , which suggests a 100x gas limit increase over two years to reach 2,000 transactions per ￰10￱ removes the previously planned EVM Object Format redesign to reduce complexity while maintaining focus on essential infrastructure ￰11￱ upgrade introduces bounded base fees for blob transactions via EIP-7918 , creating more predictable transaction costs for data-heavy ￰12￱ spam resistance and security improvements strengthen network resilience against scalability bottlenecks and ￰13￱ Implementation and Testing Timeline The Fusaka rollout follows a conservative four-phase approach across Ethereum testnets before mainnet ￰14￱ upgrade occurs October 1, followed by Sepolia on October 14 and Hoodi on October ￰15￱ testnet will undergo the complete BPO fork sequence to validate the blob capacity expansion ￰16￱ forks activate automatically based on predetermined epochs rather than requiring separate hard fork ￰17￱ mainnet, the first BPO fork launches December 17, increasing blob capacity to 10/15 target/max.

The second BPO fork activates January 7, 2026, reaching the final capacity of 14/21 ￰18￱ automated approach enables flexible blob scaling without requiring full network ￰19￱ a high-level, here's what developers agreed should be the schedule for Fusaka moving forward: October 1: Holesky upgrade October 14: Sepolia upgrade October 28: Hoodi upgrade December 3: Mainnet upgrade — Christine ￰20￱ (@christine_dkim) September 18, 2025 Notably, node operators face release deadlines ranging from September 25 for Holesky to November 3 for mainnet ￰21￱ staggered timeline, according to the developers, allows comprehensive testing while giving infrastructure providers sufficient preparation time.

Speculatively, the developers use this backward-compatible approach to ensure smooth transitions with minimal disruption to existing ￰22￱ implementation reduces node resource demands, potentially increasing network decentralization by lowering barriers for smaller ￰23￱ technology enables more efficient data availability sampling, crucial for supporting growing Layer 2 rollup adoption. Overall, these improvements, combined with increased gas limits, will enable Ethereum to handle higher transaction volumes while maintaining security ￰24￱ Network Scalability Pressures The Fusaka upgrade addresses mounting pressure for Ethereum base layer improvements amid criticism of Layer 2 fragmentation ￰25￱ argue that reliance on rollups has created isolated chains with limited interoperability, complicating user ￰26￱ upgrade’s focus on infrastructure improvements aims to enhance base layer capacity while supporting continued Layer 2 ￰27￱ recent validator queue controversy particularly highlights ongoing network scalability ￰28￱ to a Cryptonews report covered yesterday, currently, over 2M ETH sits in exit queues facing 43-day delays, while entry queues process in just 7 ￰29￱ Validator Queue () However, Vitalik Buterin defended these delays as essential for network security, comparing validator commitments to military service requiring “ friction in quitting .” The upgrade coincides with growing institutional interest in Ethereum infrastructure, with VanEck predicting that Layer 2 networks could reach $1 trillion market capitalization within six years.

Fusaka’s emphasis on data availability and node efficiency supports Ethereum’s evolution toward seamless cross-chain ￰30￱ upgrade complements initiatives like the Open Intents Framework, where Coinbase Payments recently joined as a core ￰31￱ initiative, if successful, will address the $21B surge in cross-chain ￰32￱ coordinated efforts aim to unify the fragmented multichain experience while maintaining Ethereum’s security and decentralization principles.