Catenaa, Wednesday, September 24, 2025- Ethereum developers have scheduled December 3, 2025, as the mainnet activation date for the Fusaka upgrade, moving the network’s timeline forward to address scaling and transaction capacity demands.
Testnets for Fusaka will begin in October, following findings from Devnet-5 that revealed software bugs and setup errors, limiting early capacity testing.
Fusaka introduces phased increases in blob capacity, temporary data packets used by rollups to post transaction data efficiently.
Developers plan an initial increase to 10–15 blobs per block, followed by 14–21 blobs, allowing the network to gradually handle higher transaction volumes while maintaining low fees. Devnet-6 will further validate these changes ahead of public testnets and mainnet deployment.
The upgrade also addresses issues with validator clients.
The Prysm client experienced orphaned blocks under heavy loads, while the ckzg library used for verifying blobs has been patched.
A lighter version of the library is in development to ease client team integration and reduce upgrade risks. Shadow forks and bundled releases are planned for October to ensure smooth rollout.
Fusaka follows the May 2025 Pectra upgrade, which improved staking limits, increased data capacity, and simplified Ethereum’s user experience.
While Pectra helped address early scaling pressures, growing rollup demand required additional blob capacity, prompting the accelerated Fusaka timeline.
Developers caution that delays remain possible if new bugs arise during testing or if further refinements are needed.
The upgrade highlights Ethereum’s ongoing focus on supporting decentralized applications and Layer 2 solutions while keeping transaction costs manageable, reinforcing the network’s position as a leading platform for smart contracts and decentralized finance.
