Ethereum Activates Fusaka Upgrade on Mainnet

Ethereum's long-awaited Fusaka upgrade activated on its mainnet on December 3, 2025, at approximately 2149 UTC, introducing significant enhancements to data availability and scalability that developers say will bolster the network's capacity to handle growing transaction volumes from layer 2 solutions.

The upgrade, Ethereum's second major network change this year following the Pectra update in May, went live at epoch 411392 and block height 18,200,000 after successful testing on the Holesky, Sepolia, and Hoodi test networks throughout October. Client teams conducted final readiness checks earlier in the week, ensuring a smooth rollout without disruptions for users. Core developers monitored the activation closely, with the process finalizing within minutes, as confirmed by the official Ethereum account.

At the heart of Fusaka is PeerDAS, a peer data availability sampling system that allows nodes to verify only small, randomly selected portions of blob data rather than downloading entire blocks. This reduces bandwidth and storage demands by up to 85 percent, expanding the network's blob throughput capacity by approximately eight times. Blobs are the data structures used by layer...